Sewage impacts coral reefs at multiple levels of ecological organization

Responses of plankton community to threshold metal concentrations of cadmium and lead in a mesocosm experiment at Bay of Bengal

Metals are essential at trace levels to aquatic organisms for the function of many physiological and biological processes. But their elevated levels are toxic to the ecosystem and even brings about shifts in the plankton population. Threshold limits such as Predicted No Effect Concentration (PNEC - 0.6 μg/l of Cd; 2.7 μg/l of Pb), Criterion Continuous Concentration (CCC - 3.0 μg/l of Cd; 4.5 μg/l of Pb) and Criterion Maximum Concentration (CMC - 23 μg/l of Cd; 130 μg/l of Pb) prescribed for Indian coastal waters were used for the study. Short-term mesocosm experiments (96 h) were conducted in coastal waters of Visakhapatnam to evaluate responses of the planktonic community on exposure to threshold concentrations of cadmium and lead for the first time. Four individual experimental bags of 2500 L capacity (Control, PNEC, CCC & CMC) were used for the deployment and ambient water samples were analysed simultaneously to evaluate the impacts of the threshold levels in the natural waters. Chaetoceros sp. were dominant group in the control system whereas, Prorocentrum sp. Ceratium sp. Tintinopsis sp. Chaetoceros sp. and Skeletonema sp. were major groups in the test bags. Throughout the experiment the phytoplankton community did not show any significant differences with increased nutrients and plankton biomass (Chl-a <8.64 mg/m3). Positive response of plankton community was observed in the experimental bags. High abundance of diatoms were observed in PNEC, CCC & CMC bags at 48 h and the abundance decreased with shift in the species at 72-96 h. The catalase activity in phytoplankton (5.99 nmol/min/ml) and the zooplankton (4.77 nmol/min/ml) showed induction after exposure to PNEC. The present mesocosm study is confirmed that short-term exposure to threshold metal concentration did not affects the phytoplankton community structure in PNEC, but CCC and CMC affects the community structure beyond 24 h. The insights from this study will serve as a baseline information and help develop environmental management tools. We believe that long-term mesocosm experiments would unravel metal detoxification mechanisms at the cellular level and metal transfer rate at higher trophic levels in real-world environment.

Comparison of coral reef communities in proximity to ocean effluent pipes off the north coast of Puerto Rico

Coral reefs are declining globally as a result of multiple stressors, including land-based stressors, such as sedimentation and pollution, and those that are related to a changing climate, such as increases in ocean acidification. Degradation of US Caribbean coral reef biota has been associated with exposure to sewage effluent from wastewater treatment plants (WWTPs). The Puerto Rico Aqueduct and Sewer Authority (PRASA) maintains WWTPs on the north coast of Puerto Rico, which release effluent into the marine environment in the vicinity of coral reefs. Using data collected by PRASA surveys conducted from 1999 to 2013, we examined coral reef condition at survey sites to identify potential changes or differences in reefs with respect to their proximity to the WWTP effluent pipes (e.g., upstream, downstream). The proportion of coverage represented by all coral, sensitive taxa, and tolerant taxa were compared across sites located upstream and downstream of WWTP effluent pipes using multivariate approaches and analysis of variance. The proportion of healthy, sensitive coral species and invasive or tolerant coral species were not different at sites downstream of the WWTP effluent pipe compared to upstream. These results are caveated by the limited sampling design, highly variable communities across WWTP locations, and the sparsity or absence of well-developed coral reef communities at most stations. We evaluate the strengths and weaknesses of the survey design and provide recommendations for future coral reef surveys investigating potential impacts of WWTP effluent.

Hypothetical effects assessment of tourism on coastal water quality in the Marine Tourism Park of the Gili Matra Islands, Indonesia

Tourism is one of the most important issues facing marine protected areas (MPAs) and small islands worldwide. Tourism development is considered a contribution to pollution levels in the environment. This paper aims to evaluate the hypothetical effects of tourism development on water quality spatially and temporally using the coastal water quality index (CWQI) and Geographic Information System (GIS) in search of improved management for marine conservation areas. This study showed significant tourism influences on the CWQI in the Marine Tourism Park of the Gili Matra Islands, Lombok, Indonesia. Water quality variability indicates a significant spatiotemporal difference (p < 0.05) in the two tourism seasons. During the peak season of tourism, the CWQI decreased to poor conditions, i.e., ranging from 9.95 to 21.49 for marine biota and from 7.98 to 30.42 for marine tourism activities in 2013, and ranging from 39.52 to 44.42 for marine biota and from 44.13 to 47.28 for marine tourism activities, which were below the standard for both marine biota and marine tourism activities. On the contrary, it showed a better level (from poor to moderate) during the low season of tourism (ranging from 41.92 to 61.84 for marine biota and from 48.06 to 65.27 for marine tourism activities in 2014), providing a more acceptable condition for both aspects. The study proved that massive tourism development in the MPA and small islands could reduce water quality and increase vulnerability. Accordingly, integrated tourism management and the environment, waters, and land will be needed to develop sustainable tourism. The CWQI and GIS were applicable to assess water quality, both spatially and temporally, and become a quick reference in monitoring and initial evaluation of impact management.

Biogeochemical modelling of a tropical coastal area undergoing seasonal upwelling and impacted by untreated submarine outfall

A coupled 3D hydrodynamic-ecological model was applied to the Santa Marta Coastal Area (SMCA, Colombian Caribbean) to provide insights into the role of external stressors (e.g. wastewater outfall and upwelling) on the water quality and benthic - pelagic coupling. The model was calibrated and validated based on benthic metabolic measurements, satellite-derived chlorophyll-a (Chl-a) and sea surface temperature (SST) maps, field and literature water quality data. The model was able to reproduce the complex dynamics and fast transitions of temperature, nutrients, and phytoplankton, including the stratification and mixing periods during the non-upwelling (NUPW) and upwelling (UPW) seasons. Wide and fast changes in the temperatures and the highly flushed environment prevented excess phytoplankton growth and nutrient accumulation in the benthic and pelagic compartments. The model proved to be a reliable research tool to analyze the interactive effects of upwelling and untreated wastewater on the functioning of a tropical bay.

Identifying wastewater management tradeoffs: Costs, nearshore water quality, and implications for marine coastal ecosystems in Kona, Hawai'i

Untreated and minimally treated wastewater discharged into the environment have the potential to adversely affect groundwater dependent ecosystems and nearshore marine health. Addressing this issue requires a systems approach that links land use and wastewater management decisions to potential impacts on the nearshore marine environment via changes in water quality and quantity. To that end, a framework was developed to assess decisions that have cascading effects across multiple elements of the ridge-to-reef system. In an application to Kona (Hawai'i, USA), eight land use and wastewater management scenarios were evaluated in terms of wastewater system upgrade costs and wastewater related nutrient loads in groundwater, which eventually discharge to nearshore waters, resulting in potential impacts to marine habitat quality. Without any upgrades of cesspools or the existing wastewater treatment plant (WWTP), discharges of nutrients are expected to increase substantially with permitted development, with potential detrimental impacts to the marine environment. Results suggest that converting all of the existing cesspools to aerobic treatment units (ATU) and upgrading the existing WWTP to R-1 quality provide the highest protection to nearshore marine habitat at a cost of $569 million in present value terms. Other wastewater management options were less effective but also less costly. For example, targeted cesspool conversion (a combination of septic and ATU installation) in conjunction with the WWTP upgrade still provided a substantial reduction in nutrients and potential impacts to marine habitat quality relative to the present situation at a price point roughly $100 million less than the entirely ATU option. Of note, results were more sensitive to the inclusion of the WWTP upgrade option than they were to assumptions regarding the efficiency of the cesspool conversion technologies. The model outputs also suggest that the spatial distribution of potential impacts should be carefully considered when comparing different wastewater management scenarios. When evaluated separately, the WWTP option reduced total nutrients by more than the targeted cesspool conversion option at a fraction of the cost. However, potential improvements in marine habitat quality only occurred in the immediate vicinity of the WWTP, whereas the benefits under targeted cesspool conversion were more evenly distributed along the coast.

Sources of organic matter and tracing of nutrient pollution in the coastal Bay of Bengal

Stable isotopic composition of carbon (δ¹³C_POM) and nitrogen (δ¹⁵N_POM) in the particulate organic matter (POM) is used to identify sources of organic carbon and nutrients using monthly time-series observation in the coastal Bay of Bengal (BoB). The hydrographic structure indicates that the coastal BoB is influenced by coastal upwelling during March-May, advection of peninsular river discharge during June to September and glacial (Ganges) river discharge during October to December due to reversing of East India Coastal Currents (EICC). C/N ratios in POM were mostly higher values than Redfield ratio in the study region indicating possible contribution of terrestrial origin. Enriched δ¹³C_POM were found during March-May associated with coastal upwelling indicating major contribution of POM from the in situ production while lower values were noticed during June to September followed by October to December indicating influence of terrestrial sources. δ¹⁵N_POM displayed strong inverse relation with salinity and linear relation with Chl-a suggesting that anthropogenic nutrients from the land increased coastal phytoplankton biomass. δ¹⁵N_POM linearly decreased with increase in distance from the coast and reached to the typical offshore value of 6-6.5‰ indicating that terrestrial nutrients influence was spread up to a distance of 15 to 20 km from the coast in the study region. Our study suggested that coastal waters are influenced by terrestrial/anthropogenic nutrients and its impact can be noticed up to 15 to 20 km from the coast and its impact on Biodiversity Beyond National Jurisdiction may be negligible than hitherto hypothesized.

Ecological features of a rocky intertidal community exposed to sewage effluent

Sewage is among the largest components of coastal pollution, showing a variable scale and size when causing an impact. In this study, temporal and spatial sewage-related gradients were identified using univariate and multivariate methods. Phosphates and nitrogen-based nutrients, except nitrate, were associated to sewage. Abundance and species richness decrease with distance from the sewage outfall while evenness increased. Filter-feeder bivalves and grazer crustaceans showed preference for the sewage discharge site. Gastropods were more abundant at an intermediate distance, likely reflecting primary production enhancement by sewage. Beta diversity was lower at the location and time with highest sewage loadings. The turnover component of beta diversity expressed as an absolute or proportional value was also useful to detect temporal and spatial sewage-related gradients. Highly energetic hydrodynamics contributes to ameliorate sewage impacts, yet not enough to veil the effect of pollution in this study.

Algal bioassays detect modeled loading of wastewater-derived nitrogen in coastal waters of O'AHU, HAWAI'I

Previous studies indicate coastlines are at risk of wastewater contamination from injection wells, cesspools, and septic systems. In this study, common marine algae were used to ground-truth modeled loading of wastewater-derived N to coastlines of O'ahu, Hawai'i. Macroalgae were collected and/or deployed at 118 sites and analyzed for tissue δ¹⁵N and N %. Wastewater source locations were used to estimate wastewater-derived N in groundwater with the modeling software MT3DMS/MODFLOW. Algal bioassays identified six coastal regions subjected to elevated wastewater-derived N loading. In a case study, submarine groundwater discharge (estimated by ²²²Rn mass balance) was related to wastewater loading from onsite sewage disposal systems (OSDS) and municipal wastewater injection wells in Waimānalo. The highest ²²²Rn-derived SGD rate and N flux were 21.4 m³/m/d and 62.6 g/m/d, respectively. The results of this study suggest that OSDS and injection wells discharge substantial volumes of wastewater and N across broad regions of coastal O'ahu.

Decision analysis to support wastewater management in coral reef priority area

A cocktail of land-based sources of pollution threatens coral reef ecosystems, and addressing these has become a key management and policy challenge in the State of Hawai'i, other US territories, and globally. In West Maui, Hawai'i, nearly one quarter of all living corals were lost between 1995 and 2008. Onsite disposal systems (OSDS) for sewage leak contaminants into drinking water sources and nearshore waters. In recognition of this risk, the Hawai'i State Department of Health (DOH) is prioritizing areas for cesspool upgrades. Independently, we applied a decision analysis process to identify priority areas to address sewage pollution from OSDS in West Maui, with the objective of reducing nearshore coral reef exposure to pollution. The decision science approach is relevant to a broader context of coastal areas both statewide and worldwide which are struggling with identifying pollution mitigation actions on limited budgets.

Determinants of environmental conservation in Lake Tana Biosphere Reserve, Ethiopia

This study has investigated the factors that determine the conservation of one of the major ecosystem in Ethiopia, Lake Tana Biosphere Reserve, using primarily quantitative followed by qualitative approach to provide adequate results of the problem under study. The study has employed the descriptive design and a total of 305 samples from rural households (n = 159) and tourism-related enterprises (n = 146) were selected based on a stratified random sampling technique. Samples were drawn based on their direct attachment either in their livelihood and possess a responsibility to the study area. Data were collected through questionnaires, observation, focus group discussion, unstructured interview and secondary data was consulted. Exploratory factor analysis was used to extract dimensions for environmental awareness. Binary logistic regression was used to analyze data using SPSS version 23. Ten Socio-demographic variables of samples were used as an independent variable and environmental conservation dimensions as dependent variables. The result revealed that out of the 10 variables employed in the analysis, six variables were found significant. Hence, marital status, household size, income source, household income, membership to club and resident location were found to be significant. Qualitative analysis revealed wrong reports for political consumption driven little government attention and lack of integrated natural resource management policy and plan were major factors hindering conservation. A vivid and holistic destination management policy making with enough room to stakeholders' involvement shall be a prior task for the government for better conservation of the ecosystem and sustainable development.

Whale Shark Tourism: Impacts on Coral Reefs in the Philippines

Reef-based tourism has been developing rapidly in recent decades yet its impacts on reef ecosystems are often overlooked. In Tan-awan, Oslob, Philippines, whale sharks are attracted to the shallow reefs where they are provisioned up to 50 tons y^-1 of feed and this phenomenon in turn attracts >300,000 y^-1 visitors. Given the intensive provisioning and concentrating tourism activities, we hypothesized that the whale shark tourism-impacted site (IS) will have greater impacts on reef degradation and higher anthropogenic nitrogen pollution level compared to its reference site (RS). Ecological surveys revealed that relative to the RS, the IS had 36% higher relative abundance of Pocillopora and Porites coral over other genera, >2.5-fold lower coral density, and 20% higher macroalgal cover, which we concluded are signs of reef degradation. Also, we conducted stable nitrogen isotope analysis on gorgonian skeletons to trace nitrogen sources at both sites through time. Although an average 1‰ isotope enrichment found in the IS relative to the RS could indicate anthropogenic nitrogen inputs in the IS, this enrichment was consistent over time and existed before the tourism developed. Despite that, we cautioned against the imminent threat of local eutrophication caused by the continued inputs of nitrogen derived from provisioning and tourism activities. In summary, this study provided the first documentation of the impacts of provisioned whale shark tourism on the local reefs in Tan-awan and established an ecological baseline for future comparisons. Such assessments can offer important information on reef health, coastal development, and tourism management.

Pollution status of marine protected areas worldwide and the consequent toxic effects are unknown

Chemical pollution is considered a factor that may threaten marine protected areas (MPAs), and recent studies have found contamination and associated biological effects in some MPAs. However, organized data on this topic are lacking. This study reviewed the literature on pollution in MPAs in order to compile data, determine whether MPAs are influenced by pollution and, whenever possible, describe how they are being affected by contaminants. The results show that the pollution status is unknown in most MPAs worldwide. When any information is available, it is often insufficient to diagnose the threats to biodiversity or to support further actions. More robust and extensive information is available on a small number of MPAs, and much less information is available regarding the negative effects of pollution. More than 80% of the areas studied exhibited evidence of contamination at potentially toxic concentrations or were found to have a status that produced toxic effects on the biota. The scientific community is encouraged to study pollution in MPAs worldwide.

Research gaps of coral ecology in a changing world

Coral reefs have long inspired marine ecologists and conservationists around the world due to their ecological and socioeconomic importance. Much knowledge on the anthropogenic impacts on coral species has been accumulated, but relevant research gaps on coral ecology remain underappreciated in human-modified seascapes. In this review we assessed 110 studies on coral responses to five major human disturbances- acidification, climate change, overfishing, pollution and non-regulated tourism -to identify geographic and theoretical gaps in coral ecology and help to guide further researches on the topic. We searched for papers in Web of Science published from 2000 to 2016 and classified them according to the ocean, ecoregion, human threat, level of biological organization, study approach, method of data collection, depth of data collected, and type of coral response. Most studies were carried out in the Indo-Pacific and Caribbean (36.3 and 31.9%, respectively) and used observational approach (60%) with scuba diving (36.3%) to assess the impact of ocean warming (55.4%) on coral communities (58.2%). Only 37 of the 141 global ecoregions that contain coral reefs were studied. All studies were restricted to shallow waters (0.5-27 m depth) and reported negative responses of corals to human disturbance. Our results reinforce the notion that corals are sensitive to anthropogenic changes. They reveal the scarcity of information on coral responses to pollution, tourism, overfishing and acidification, particularly in mesophotic ecosystems (>30 m depth) and in ecoregions outside the Indo-Pacific and Caribbean. Experimental studies at the individual and population levels should be also encouraged.

Spatial distribution of sewage pollution on a Hawaiian coral reef

While sewage pollution is contributing to the global decline of coral reefs, its offshore extent and direct reef impacts from water column mixing and benthic seeps are poorly documented. We addressed this knowledge gap on a Hawaiian coral reef using sewage indicator and benthic cover measurements, macroalgal bioassays, and a pollution scoring tool. Fecal indicator bacteria (FIB) and nutrient concentrations were spatially variable in surface and benthic waters, with shoreline values being highest. Shoreline macroalgae δ¹⁵N and %N indicated high nitrogen loads containing sewage, while offshore surface and benthic values suggested lower nitrogen loads from environmental sources. Coral cover was negatively correlated with FIB, macroalgal δ¹⁵N, and nutrient concentrations. Benthic salinity and temperature measurements detected daily tidal groundwater pulses which may explain these associations. While pollution scores revealed that sewage was largely concentrated along the shoreline, results showed some reached the reef and may be contributing to its declining condition.

Compositional shifts in bacterial communities associated with the coral Palythoa caribaeorum due to anthropogenic effects

Corals harbor abundant and diverse prokaryotic communities that may be strongly influenced by human activities, which in turn compromise the normal functioning of coral species and predispose them to opportunistic infections. In this study, we investigated the effect of sewage dumping on the bacterial communities associated with the soft coral Palythoa caribaeorum at two sites in the Brazilian coast. We observed a dominance of bacterial species classified as human pathogens at sites exposed to untreated sewage discharge. The microbial diversity of undisturbed sites was more homogeneous and diverse and showed greater abundance. In addition, bacterial communities differed substantially between the exposed and undisturbed areas. The microbial community associated with the samples collected from the exposed sites revealed the anthropogenic effect caused by organic matter from untreated sewage dumping, with an abundance of pathogenic bacterial species.

Ecological carrying capacity assessment of diving site: A case study of Mabul Island, Malaysia

Despite considered a non-consumptive use of the marine environment, diving-related activities can cause damages to coral reefs. It is imminent to assess the maximum numbers of divers that can be accommodated by a diving site before it is subject to irreversible deterioration. This study aimed to assess the ecological carrying capacity of a diving site in Mabul Island, Malaysia. Photo-quadrat line transect method was used in the benthic survey. The ecological carrying capacity was assessed based on the relationship between the number of divers and the proportion of diver damaged hard corals in Mabul Island. The results indicated that the proportion of diver damaged hard corals occurred exponentially with increasing use. The ecological carrying capacity of Mabul Island is 15,600-16,800 divers per diving site per year at current levels of diver education and training with a quarterly threshold of 3900-4200 per site. Our calculation shows that management intervention (e.g. limiting diving) is justified at 8-14% of hard coral damage. In addition, the use of coral reef dominated diving sites should be managed according to their sensitivity to diver damage and the depth of the reefs.

Coral reef fish assemblages along a disturbance gradient in the northern Persian Gulf: A seasonal perspective

Seasonal dynamics of coral reef fish assemblages were assessed along a gradient of potential anthropogenic disturbance in the Northern Persian Gulf. Overall, the attributes of coral reef fish assemblages showed seasonality at two different levels: seasonal changes irrespective of the magnitude of disturbance level (e.g. species richness), and seasonal changes in response to disturbance level (e.g. total abundance and assemblage composition). The examined parameters mostly belonged to the second group, but the interpretation of the relationship between patterns of seasonal changes and the disturbance level was not straightforward. The abundance of carnivorous fishes did not vary among seasons. SIMPER identified the family Nemipteridae as the major contributor to the observed spatiotemporal variations in the composition of coral reef fish assemblages in the study area.

Decline in abundance and health state of an Atlantic subtropical gorgonian population

Losses in coral cover have been widely reported for the Caribbean. In contrast, much less is known about the health state of the Brazilian reef fauna, which was declared as a priority for Atlantic biodiversity conservation due to its high degree of endemism. In the present study, we assessed the general health state of Phyllogorgia dilatata assemblages at the subtropical reefs of Arraial do Cabo (southeastern Brazil), where observations suggest that the abundance of this endemic gorgonian species has declined. We found that about 49% of the sampled colonies were dead, and 73% of the living colonies were affected by tissue loss. Tissue loss initially manifested as multifocal holes in the planar colonial coenenchyme and peripheral tissue retraction leaving denuded skeletal axes. In combination with other recent studies, our results raise the awareness for an increasingly threatened Southwestern Atlantic reef coral fauna.

Sewage pollution: mitigation is key for coral reef stewardship

Coral reefs are in decline worldwide, and land-derived sources of pollution, including sewage, are a major force driving that deterioration. This review presents evidence that sewage discharge occurs in waters surrounding at least 104 of 112 reef geographies. Studies often refer to sewage as a single stressor. However, we show that it is more accurately characterized as a multiple stressor. Many of the individual agents found within sewage, specifically freshwater, inorganic nutrients, pathogens, endocrine disrupters, suspended solids, sediments, and heavy metals, can severely impair coral growth and/or reproduction. These components of sewage may interact with each other to create as-yet poorly understood synergisms (e.g., nutrients facilitate pathogen growth), and escalate impacts of other, non-sewage–based stressors. Surprisingly few published studies have examined impacts of sewage in the field, but those that have suggest negative effects on coral reefs. Because sewage discharge proximal to sensitive coral reefs is widespread across the tropics, it is imperative for coral reef–focused institutions to increase investment in threat-abatement strategies for mitigating sewage pollution.

Response of a seagrass fish assemblage to improved wastewater treatment

We compared the structure of a seagrass fish assemblage near a sewage outlet before and after improvements to wastewater treatment. To determine whether responses by the fish assemblage were due to changes in water quality or to other factors, comparisons were made with the structure of a fish assemblage from a nearby site unaffected by sewage effluent. Total species richness, density and biomass of fish, decreased at both sites over the 30-year period. An increase in mean trophic level near the sewage outlet following improvements in water quality indicated that wastewater treatment had another important effect. This result is consistent with the reductions in food webs supporting pelagic and benthic fishes that typically accompany decreases in nutrient inputs. Although improvements to wastewater treatment explained much of the variation in the structure of the fish assemblage at PC, our results also suggest that fishing and climate change, at both sites.

Improving the construction of functional models of alternative persistent states in coral reefs using insights from ongoing research programs: a discussion paper

Extensive degradation of coral reefs makes it imperative to create functional models that demonstrate ecological processes which occur in alternative states that persist over time. These models provide important information that can help in decision making regarding management measures for both the prevention of further degradation and the recovery of these ecosystems. Development of these models requires identifying and testing the ecological processes that will impose the reduction of coral cover and, preferably, identifying the disturbance that triggers this phenomenon. For this reason, research programs are a useful tool which allows a focus on the production of information for modeling. It should start with survey investigations and tests of hypotheses concerning the cause of the reduction of coral cover. Subsequently, projects should be guided by the most probable hypotheses, focusing on one guild or functional group at a time until the "trigger" process which unleashed the disturbance is identified. Even if incomplete, these models already provide information for focusing management steps.

Tolerance of Brazilian brain coral Mussismilia braziliensis to sediment and organic matter inputs

In Brazil, where reefs occur in markedly turbid environments, the relationship between sedimentation/organic matter and corals is poorly known. Thus, the ex situ effects of sediment with and without organic matter over the ΔF/Fm and physical state of Mussismilia braziliensis were analyzed. The ΔF/Fm and coral physical state, evaluated through the susceptibility index to sedimentation (SI), were measured in seven colonies exposed to sedimentation (0-450 mg cm(-2) day(-1)) free of organic matter after 45 days of exposure, and in 12 colonies exposed to sedimentation (0-500 mg cm(-2) day(-1)) with organic matter content (10%), in which case ΔF/Fm was measured after 72 h and SI after 120 h. In both cases there were effects of increasing sedimentation on the SI with no effect on ΔF/Fm. Despite the tolerance to high sedimentation rates shown by this coral, we noted that the presence of organic matter might reduce its tolerance to sedimentation stress.

High congruence of isotope sewage signals in multiple marine taxa

Assessments of sewage pollution routinely employ stable nitrogen isotope analysis (δ(15)N) in biota, but multiple taxa are rarely used. This single species focus leads to underreporting of whether derived spatial N patterns are consistent. Here we test the question of 'reproducibility', incorporating 'taxonomic replication' in the measurement of δ(15)N gradients in algae, seagrasses, crabs and fish with distance from a sewage outfall on the Adelaide coast (southern Australia). Isotopic sewage signals were equally strong in all taxa and declined at the same rate. This congruence amongst taxa has not been reported previously. It implies that sewage-N propagates to fish via a tight spatial coupling between production and consumption processes, resulting from limited animal movement that closely preserves the spatial pollution imprint. In situations such as this where consumers mirror pollution signals of primary producers, analyses of higher trophic levels will capture a broader ambit of ecological effects.

Measuring restoration in intertidal macrophyte assemblages following sewage treatment upgrade

Understanding the effectiveness of pollution mitigation actions in terms of biological recovery is essential if the environmental protection goals of management policies are to be achieved. Few studies, however, have evaluated the restoration of seaweed assemblages following pollution abatement. This study aimed to investigate the response of macroalgal vegetation to the upgrade of a wastewater treatment plant using a "Beyond BACI" experimental design. Temporal differences in vegetation structure between the outfall and two control locations over a 10-year period were assessed. Improvement in sewage treatment was found to lead to increases in diversity, cover of morphologically complex algae and spatial heterogeneity. The multivariate composition of assemblages at the outfall location became more similar to that at the controls; however, their complete recovery may depend on factors other than pollution removal. Our findings also suggest that the extent of restoration and the time required to detect it are largely predetermined by the response variables we choose to assess recovery.

Evolutionary insights into scleractinian corals using comparative genomic hybridizations

Background

Coral reefs belong to the most ecologically and economically important ecosystems on our planet. Yet, they are under steady decline worldwide due to rising sea surface temperatures, disease, and pollution. Understanding the molecular impact of these stressors on different coral species is imperative in order to predict how coral populations will respond to this continued disturbance. The use of molecular tools such as microarrays has provided deep insight into the molecular stress response of corals. Here, we have performed comparative genomic hybridizations (CGH) with different coral species to an Acropora palmata microarray platform containing 13,546 cDNA clones in order to identify potentially rapidly evolving genes and to determine the suitability of existing microarray platforms for use in gene expression studies (via heterologous hybridization).

Results

Our results showed that the current microarray platform for A. palmata is able to provide biological relevant information for a wide variety of coral species covering both the complex clade as well the robust clade. Analysis of the fraction of highly diverged genes showed a significantly higher amount of genes without annotation corroborating previous findings that point towards a higher rate of divergence for taxonomically restricted genes. Among the genes with annotation, we found many mitochondrial genes to be highly diverged in M. faveolata when compared to A. palmata, while the majority of nuclear encoded genes maintained an average divergence rate.

Conclusions

The use of present microarray platforms for transcriptional analyses in different coral species will greatly enhance the understanding of the molecular basis of stress and health and highlight evolutionary differences between scleractinian coral species. On a genomic basis, we show that cDNA arrays can be used to identify patterns of divergence. Mitochondrion-encoded genes seem to have diverged faster than nuclear encoded genes in robust corals. Accordingly, this needs to be taken into account when using mitochondrial markers for scleractinian phylogenies.

Detecting human mitigation intervention: effects of sewage treatment upgrade on rocky macrofaunal assemblages

The effectiveness of secondary vs primary treatments of wastewaters in mitigating the effects of sewage discharge on the multivariate structure and diversity of rocky invertebrate assemblages was assessed over a nine-year period through a beyond-BACI experimental design. Assemblages from different tidal levels (i.e. mid-shore, low-shore, 3 m and 8 m subtidal) were sampled at the impact location (I) and three control locations (Cs) at a hierarchy of spatial scales. The improvement in water treatment significantly changed the structure, diversity and cover of low intertidal assemblages. Faunal cover at 8 m subtidal increased significantly after the treatment upgrade at I. The secondary treatment also affected patterns of spatial heterogeneity between I and Cs for mid-shore and 3 m subtidal assemblages. This study demonstrates that powerful experimental designs combined with univariate and multivariate analytical approaches are fundamental in distinguishing the subtle effects of human impact from those of natural processes.

Excreted thiocyanate detects live reef fishes illegally collected using cyanide--a non-invasive and non-destructive testing approach

Cyanide fishing is a method employed to capture marine fish alive on coral reefs. They are shipped to markets for human consumption in Southeast Asia, as well as to supply the marine aquarium trade worldwide. Although several techniques can be used to detect cyanide in reef fish, there is still no testing method that can be used to survey the whole supply chain. Most methods for cyanide detection are time-consuming and require the sacrifice of the sampled fish. Thiocyanate anion (SCN⁻) is a metabolite produced by the main metabolic pathway for cyanide anion (CN⁻) detoxification. Our study employed an optical fiber (OF) methodology (analytical time <6 min) to detect SCN⁻ in a non-invasive and non-destructive manner. Our OF methodology is able to detect trace levels (>3.16 µg L⁻¹) of SCN⁻ in seawater. Given that marine fish exposed to cyanide excrete SCN⁻ in the urine, elevated levels of SCN⁻ present in the seawater holding live reef fish indicate that the surveyed specimens were likely exposed to cyanide. In our study, captive-bred clownfish (Amphiprion clarkii) pulse exposed for 60 s to either 12.5 or 25 mg L⁻¹ of CN⁻ excreted up to 6.96±0.03 and 9.84±0.03 µg L⁻¹ of SCN⁻, respectively, during the 28 days following exposure. No detectable levels of SCN⁻ were recorded in the water holding control organisms not exposed to CN⁻, or in synthetic seawater lacking fish. While further research is necessary, our methodology can allow a rapid detection of SCN⁻ in the holding water and can be used as a screening tool to indicate if live reef fish were collected with cyanide.

The impact of coastal urbanization on the structure of phytobenthic communities in southern Brazil

The anthropogenic pressures on coastal areas represent important factors affecting local, regional, and even global patterns of distribution and abundance of benthic organisms. This report undertakes a comparative analysis of the community structure of rocky shore intertidal phytobenthos in both pristine like environments (PLE) and urbanized environments (UBE) in southern Brazil, characterizing variations on different spatial scales. Multivariate analysis of variance indicated that the PLE is characterized by a larger number of taxa and an increased occurrence of Rhodophyta species in relation to UBE. In contrast, UBE were dominated by opportunistic algae, such as Cladophora and Ulva spp. Significance tests further indicated higher species richness and Shannon-Wiener diversity on the PLE in relation to UBE. Here we provide data showing the magnitude of seaweed biodiversity loss and discuss direct and indirect consequences of unplanned urbanization on these communities.

High levels of sediment contamination have little influence on estuarine beach fish communities

While contaminants are predicted to have measurable impacts on fish assemblages, studies have rarely assessed this potential in the context of natural variability in physico-chemical conditions within and between estuaries. We investigated links between the distribution of sediment contamination (metals and PAHs), physico-chemical variables (pH, salinity, temperature, turbidity) and beach fish assemblages in estuarine environments. Fish communities were sampled using a beach seine within the inner and outer zones of six estuaries that were either heavily modified or relatively unmodified by urbanization and industrial activity. All sampling was replicated over two years with two periods sampled each year. Shannon diversity, biomass and abundance were all significantly higher in the inner zone of estuaries while fish were larger on average in the outer zone. Strong differences in community composition were also detected between the inner and outer zones. Few differences were detected between fish assemblages in heavily modified versus relatively unmodified estuaries despite high concentrations of sediment contaminants in the inner zones of modified estuaries that exceeded recognized sediment quality guidelines. Trends in species distributions, community composition, abundance, Shannon diversity, and average fish weight were strongly correlated to physico-chemical variables and showed a weaker relationship to sediment metal contamination. Sediment PAH concentrations were not significantly related to the fish assemblage. These findings suggest that variation in some physico-chemical factors (salinity, temperature, pH) or variables that co-vary with these factors (e.g., wave activity or grain size) have a much greater influence on this fish assemblage than anthropogenic stressors such as contamination.

Sewage pollution impact on Mediterranean rocky-reef fish assemblages

The effects of sewage outfalls on subtidal fish assemblages were studied along the NW coasts of Malta (Sicily channel, Mediterranean Sea) by means of underwater visual census. The presence of two spatially distinct outfalls discharging untreated wastewaters allowed to use a balanced symmetrical after control/impact (ACI) design that consisted of two putatively impacted locations and two controls, with four sites nested in each location. Surveys were performed in 2006 at two random dates. The study highlighted significant changes at both assemblage and individual species levels. Fish assemblages structures were different between controls and sewages, where total abundance of fish were higher. The responses of individual species to sewage pollution were mostly related to an anomalous increase of two small opportunistic species i.e. Gobius bucchichii and Parablennius rouxi and to a decrease of species of the genus Symphodus, particularly S. roissali and S. ocellatus. Moreover in correspondence of the outfalls, significant changes of the fish size distribution were detected for several species. These results support the use of fish assemblages as biological indicators for marine coastal waters and demonstrated the possibility to obtain sharp signals of environmental impact from some individual fish species.

Wastewater discharge degrades coastal waters and reef communities in southern Thailand

Runoff and sewage discharge from land developments can cause significant changes in water quality of coastal waters, resulting in coral degradation. Coastal waters around Phuket, Thailand are influenced by numerous sewage outfalls associated with rapid tourism development. Water quality and biological monitoring around the Phuket region was undertaken to quantify water quality and biotic characteristics at various distances from sewage outfalls. The surveys revealed strong gradients in water quality and biotic characteristics associated with tourism concentration levels as well as seasonal variability. Water and reef quality tended to decrease with increasing tourist intensity, but improved with increasing distance from sewage discharge within each of the three study locations. In addition, the effect of wastewater discharge was not localised around the source of pollution, but appeared to be transported to non-developed sites by currents, and exacerbated in the wet season.