Artificial structures in sediment-dominated estuaries and their possible influences on the ecosystem

Buoys are non-indigenous fouling hotspots in marinas regardless of their environmental status and pressure

Marinas contribute to the degradation of coastal ecosystems, constitute non-indigenous species (NIS) hotspots and function as steppingstones in invasion processes. These often enclose highly modified water bodies that promote the concentration of pollutants and propagules, favoring NIS abundance. In these habitats, floating structures are often the most invaded by fouling NIS. This study aims to address the effect of floating substrate (buoys vs pontoons) on fouling assemblages, with special focus on NIS, in 6 marinas of Cadiz Bay during summer and winter seasons. Since the effect substrate type can depend on the water physicochemical conditions and environmental state and pressures of marinas, an environmental assessment was carried out for each marina using literature, physicochemical water measurements and environmental risk assessments. Despite the registered seasonal variation in fouling assemblages and the environmental variability among the studied marinas, the type of substrate played a key role in fouling assemblages' structure and abundance. The higher abundance of fouling assemblages in buoys than pontoons favor NIS prevalence in marinas and increase the risk of NIS dispersal, particularly considering that buoys are more likely to detach and drift at sea than pontoons. The results indicate that high-risk consideration should be given to this substrate type and that the potential environmental effects of biological pollution must be considered in risk assessments.

Predation facilitates the abundance of biofouling non-indigenous species in estuarine marinas in NE Atlantic Portugal

Harbours are highly modified habitats that differ from natural areas. They are hotspots of non-indigenous species (NIS) and act as stepping-stones in invasive processes. However, local communities can exert biotic resistance against biological invasions through trophic interactions and competition. This study assesses the biotic effects of predation on the recruitment of fouling assemblages in three marinas of NE Atlantic Portugal (Cascais, Setúbal and Sines), with particular emphasis on NIS, using predator exclusion experiments. Predation increased the relative abundance of NIS, mainly Watersipora subatra, in the estuarine marinas of Cascais and Setúbal, while no predation effects were registered in the coastal marina of Sines. Therefore, predation can increase the risk of NIS invasion (biotic facilitation). Furthermore, local ecosystems may have different effects and differ in vulnerability against NIS invasions. Finally, a better understanding of coastal invasive ecology and biotic effects in coastal artificial habitats will improve our capacity for NIS management.

Two facets of geotextiles in coastal ecosystems: Anti- or profouling effects?

Nonwoven geotextile fabrics have physical, mechanical and hydraulic properties useful in coastal protection as an alternative to natural stone, slag, and concrete. In a 10-month experiment, the colonisation of macrofouling organisms on different substrata based on polypropylene (PP), polyester (PET) or high density polyethylene (HDPE) fibres was investigated in the Lagoon of Venice, Italy - an environment with temperate transitional waters with high biodiversity - and compared with the colonisation on wood as a reference substratum, because of its occurrence in artificial structures at the study location, until a stable stage was reached in the development of the macrofouling community. Geotextile fabrics showed implications for community development. They affected both ecological succession in different ways by disturbing biofouling settlement and growth (HDPE fabrics) or favouring species which become dominant (PP fabrics). For these two-faceted aspects that potentially cause different long-term impacts on the biodiversity of resident communities, the use of geotextile fabrics as antifouling or as profouling systems for restoration of degraded ecosystems is discussed. In all cases, the communities displayed unique properties, such as differences in the settlement of pioneer species, an initial disturbance to serpulid settlement, absence of barnacles, selection of dominant taxa (ascidians), and changes in the percentages of various taxa forming the community structure. Given the increasing interest in geotextile materials for employment in various marine developments and industries, these results could represent first lines of evidence to inform decision-making to minimise/modify biofouling, and/or predict the use of artificial substrata as habitats by marine organisms.

Oxidative stress sensing and response in neural stem cell fate

Neural stem/progenitor cells (NSPCs) contribute to the physiological cellular turnover of the adult brain and make up its regenerative potential. It is thus essential to understand how different factors influence their proliferation and differentiation to gain better insight into potential therapeutic targets in neurodegenerative diseases and traumatic brain injuries. Recent evidences indicate the roles of redox stress sensing and coping mechanisms in mediating the balance between NSPC self-renewal and differentiation. Such mechanisms involve direct cysteine modification, signaling and metabolic reprogramming, epigenetic alterations and transcription changes leading to adaptive responses like autophagy. Here, we discuss emerging findings on the involvement of redox sensors and effectors and their mechanisms in influencing changes in cellular redox potential and NSPC fate.

An Assessment of Computational Fluid Dynamics as a Tool to Aid the Design of the HCMR-Artificial-ReefsTM Diving Oasis in the Underwater Biotechnological Park of Crete

Since recreational diving activities have increased in recent decades, resulting in additional environmental pressure on the coastal zone, the deployment of artificial reefs as a conservation strategy to divert mass ecotourism from fragile natural reefs has been proposed and realized in many areas of the world. Twelve units of a patented naturoid artificial reef technology developed by the Hellenic Centre for Marine Research (HCMR) were deployed in 2015 in the Underwater Biotechnological Park of Crete (UBPC) in order to create an experimental diving oasis and investigate the potential of achieving this aim for the over-exploited coastal ecosystems of this part of the Eastern Mediterranean. Assessment of the degree of establishment of artificial reefs and their ability to mimic natural ecosystems is often monitored through biological surveys and sampling. The measurement of the chemical, physical, and hydrodynamic characteristics of the water mass surrounding artificial reefs is also essential to fully understand their comparison to natural reefs. In particular, the flow field around reefs has been shown to be one of the most important physical factors in determining suitable conditions for the establishment of a number of key species on reef habitats. However, the combination of biological establishment monitoring and realistic flow-field simulation using computational fluid dynamics as a tool to aid in the design improvement of already existing reef installations has not been fully investigated in previous work. They are often reported separately as either ecological or engineering studies. Therefore, this study examined a full-scale numerical simulation of the field flow around individual already installed naturoid reef shapes, and part of their present arrangement on the sea bottom of the UPBC combined with the field-testing of the functionality of the installed artificial reefs concerning fish species aggregation. The results show that the simulated flow characteristics around the HCMR diving oasis artificial reefs were in good general agreement with the results of former studies, both for flows around a single deployed unit and for flows around a cluster of more than one unit. The results also gave good indications of the performance of individual reef units concerning key desirable characteristics such as downstream shadowing and sediment/nutrient upwelling and resuspension. In particular, they confirmed extended low flow levels (less than 0.3 m/s) and in some cases double vortexes on the downstream side of reef units where observed colonization and habitation of some key fish species had taken place. They also showed how the present distribution of units could be optimized to perform better as an integrated reef cluster. The use of computational fluid dynamics, with field survey data, is therefore suggested as a useful design improvement tool for installed reef structures and their deployment arrangement for recreational diving oases that can aid the sustainable development of the coastal zone.

Aligning biodiversity conservation and ecosystem services in spatial planning: Focus on ecosystem processes

Although the consideration of socio-economic demands with biodiversity conservation is now high on the environmental policy agenda, it is not yet standard practice in spatial planning. This is argued to be related, among others, to a lack of awareness among stakeholders and practitioners of the underpinning role of ecosystem functioning and biodiversity to support human well-being. Meanwhile, there is mounting critique on the absolute focus of biodiversity conservation on static properties such as species and habitats. The establishment of more ecologically sensible objectives that include ecosystem processes besides species and habitats is put forward as a more effective way of environmental conservation. Methodological approaches increasingly consider ecosystem processes. However, the processes that are included mostly relate to aspects of biodiversity such as dispersal and productivity, and rarely do they include abiotic mechanisms that underlie biodiversity. We here report on the development of a method that integrates two principles which we identify as key to advance the integration of ecosystem services with biodiversity conservation in planning practice: (1) consider the variety of ecosystem processes, biotic as well as abiotic, that support biodiversity and ecosystem services, and (2) link the ecosystem processes to biodiversity and to socio-economic benefits to identify the common ground between seemingly conflicting objectives. The methodology uses a stepwise approach and is based on an extensive review of available knowledge on ecosystem functioning, expert consultation and stakeholder involvement. We illustrate how the methodology supports the setting of strategic goals to accomplish a healthy coastal ecosystem in Belgium, and exemplify how this may affect spatial plans. The aim of this paper is to demonstrate how including processes opens opportunities to align biodiversity and ecosystem services and how this increases chances to provide long-term benefits for biodiversity and human well-being. The paper may provide inspiration to advance current spatial planning approaches.

Marine invertebrate larvae love plastics: Habitat selection and settlement on artificial substrates

Global urbanization and plastic pollution has increased the availability and variety of substrates for sessile organisms, and are intensively used by invasive species for settlement. Despite extensive literature describing the strong association between artificial structures and invasive species, little effort has been directed towards identifying the larval traits that favor this selection. Larval selection and settlement are crucial as larvae actively search and interpret environmental cues to identify suitable habitats to settle. The aim of this research was to investigate if invertebrate larvae have a preference for a particular anthropogenic substrate, and how pre-settlement behaviors vary when encountering different substrates. We used two invasive bryozoan species, Bugula flabellata and Bugula neritina, which are commonly found in urbanized areas around the world. Energy expenditure during planktonic and benthonic stages, pre-settlement swimming/exploring behaviors, settlement and larval selectivity were quantified under laboratory conditions on different substrates (concrete, wood, polystyrene, polyvinyl chloride, polyethylene terephthalate and polycarbonate). The energy expenditure measured was higher in planktonic larvae than in early settled larvae. Larvae of both species swam less and explored more when exposed to plastic surfaces, suggesting a preference for this substrate and resulting in lower energy expenditures associated with searching for habitat. Larvae actively chose to settle on plastics rather than on wood or concrete substrates. The results suggest that for Bugula larvae, the likelihood of colonizing plastic surfaces is higher than other materials commonly found in urbanized coastal areas. The more quickly they adhere to artificial substrates the lower the energy expenditure, contributing to higher fitness in these individuals. The strong preference of invertebrate larvae for plastics can potentially extend the distribution range of many invasive marine species as they are able to travel long distances attached to floating debris. This phenomenon will likely exacerbate the introduction of exotic species into novel habitats.

Monthly population density and structure patterns of an endangered seahorse Hippocampus capensis: a comparison between natural and artificial habitats

This study investigated aspects of the population ecology of the endangered Knysna seahorse Hippocampus capensis within different habitat types. High densities of H. capensis were found within artificial Reno mattress habitat, within the Knysna Estuary, South Africa. Monthly surveys at three sites were conducted from October 2015 to August 2016 to compare population densities of H. capensis in this artificial habitat with natural eel grass Zostera capensis habitat. Hippocampus capensis densities varied significantly across all sites and highest population densities were consistently observed within the Reno mattress habitat. Hippocampus capensis were also found to be significantly larger within the Reno mattress habitat and pooled data showed that males were significantly larger than females. The overall sex ratio for all three sites was female biased, although this varied across seasons at two sites. The findings suggest that artificial Reno mattresses provide novel habitat for this endangered species and consideration should be given to the usefulness of these structures in future conservation actions.

Altered fish community and feeding behaviour in close proximity to boat moorings in an urban estuary

Coastal urbanization has led to large-scale transformation of estuaries, with artificial structures now commonplace. Boat moorings are known to reduce seagrass cover, but little is known about their effect on fish communities. We used underwater video to quantify abundance, diversity, composition and feeding behaviour of fish assemblages on two scales: with increasing distance from moorings on fine scales, and among locations where moorings were present or absent. Fish were less abundant in close proximity to boat moorings, and the species composition varied on fine scales, leading to lower predation pressure near moorings. There was no relationship at the location with seagrass. On larger scales, we detected no differences in abundance or community composition among locations where moorings were present or absent. These findings show a clear impact of moorings on fish and highlight the importance of fine-scale assessments over location-scale comparisons in the detection of the effects of artificial structures.

Insights into the establishment of the Manila clam on a tidal flat at the southern end of an introduced range in Southern California, USA

Coastal ecosystem modifications have contributed to the spread of introduced species through alterations of historic disturbance regimes and resource availability, and increased propagule pressure. Frequency of occurrence of the Manila clam (Venerupis phillipinarum, Veneridae) in Southern California estuaries has increased from absent or sparse to common since the mid-1990s. Potential invasion vectors include seafood sales and aquaculture, and spread from established northern populations over decades. The clam's post-settlement habitat preferences are, however, uncertain in this region. Our project aimed to identify factors associated with established patches of the clam within a bay toward the southern end of this introduced range. During summer 2013, we sampled 10 tidal flat sites in Mission Bay, San Diego; each containing an area with and without hard structure (e.g., riprap, boulders). We measured likely environmental influences (e.g., sediment variables, distance to ocean). Manila clam densities across the bay were most strongly associated with site, where highest densities were located in the northern and/or back halves of the bay; and weakly correlated with lower porewater salinities. Within sites, Manila clam density was enhanced in the presence of hard structure in most sites. Prevailing currents and salinity regimes likely contribute to bay wide distributions, while hard structures may provide suitable microhabitats (refuge from predators and physical stress) and larval entrapment within sites. Results provide insights into decisions about future shoreline management efforts. Finally, we identify directions for future study to better understand and therefore predict patterns of establishment of the Manila clam in the southern portion of its introduced range.