Patterns of species and functional diversity of macrofaunal assemblages and the bioassessment of benthic ecological quality status in the southern Yellow Sea

Temperature and nutrients alter the relative importance of stochastic and deterministic processes in the coastal macroinvertebrates biodiversity assembly on long-time scales

Macroinvertebrates play a vital role in coastal ecosystems and are an important indicator of ecosystem quality. Both anthropogenic activity and environmental changes may lead to significant changes in the marine macroinvertebrate community. However, the assembly process of benthic biodiversity and its mechanism driven by environmental factors at large scales remains unclear. Here, using the benthic field survey data of 15 years at large spatial and temporal scales from the Yellow Sea Large Marine Ecosystem, we investigated the relative importance of environmental selection, dispersal processes, random-deterministic processes of macroinvertebrates community diversity assembly, and the responses of this relative importance driven by temperature and nutrients. Results showed that the macroinvertebrates community diversity is mainly affected by dispersal. Nitrogen and phosphorus are the most important negative factors among environmental variables, while geographical distance is the main limiting factor of β diversity. Within the range of 0.35-0.70 mg/L of nutrients, increasing nutrient concentration can significantly facilitate the contribution of the decay effect to β diversity. Within the temperature range studied (15.0-18.0°C), both warming and cooling can lead to a greater tendency for species diversity assembly processes to be dominated by deterministic processes. The analysis contributes to a better understanding of the assembly process of the diversity of coastal marine macroinvertebrates communities and how they adapt to global biogeochemical processes.

Ecology of Saline Watersheds: An Investigation of the Functional Communities and Drivers of Benthic Fauna in Typical Water Bodies of the Irtysh River Basin

In this study, we investigated how changes in salinity affect biodiversity and function in 11 typical water bodies in the Altai region. The salinity of the freshwater bodies ranged from 0 to 5, the brackish water salinities ranged from 5 to 20, and the hypersaline environments had salinities > 20. We identified 11 orders, 34 families, and 55 genera in 3061 benthic samples and classified them into 10 traits and 32 categories. Subsequently, we conducted Mantel tests and canonical correlation analysis (CCA) and calculated biodiversity and functional diversity indices for each sampling site. The results indicated that biodiversity and the proportion of functional traits were greater in freshwater environments than in saline environments and decreased gradually with increasing salinity. Noticeable shifts in species distribution were observed in high-salinity environments and were accompanied by specific functional traits such as swimming ability, smaller body sizes, and air-breathing adaptations. The diversity indices revealed that the species were more evenly distributed in high-diversity environments under the influence of salinity. In contrast, in high-salinity environments, only a few species dominated. The results suggested that increasing salinity accelerated the evolution of benthic communities, leading to reduced species diversity and functional homogenization. We recommend enhancing the monitoring of saline water resources and implementing sustainable water resource management to mitigate the impact of salinity stress on aquatic communities in response to climate-induced soil and water salinization.

Responses of biological traits of macrobenthic fauna to a eutrophication gradient in a semi-enclosed bay, China

The impacts of eutrophication on benthic ecological functions are of increasing concern in recent years. In order to assess the response of macrobenthic fauna to increasing eutrophication, two field sampling surveys were conducted during the summer (July-August 2020) and autumn (October-November 2020) from offshore, nearshore to estuarine sediments in Bohai Bay, northern China. Biological trait analysis was employed for the assessment of macrofaunal samples. The results indicated that there was an increase in the proportion of benthic burrowering or tube-dwelling sediment feeders and taxa with higher larval dispersal ability, but a decrease in the proportion of taxa showing high motility in areas with higher nutrient levels. Seasonal differences were also noted in the shift in biological traits, with a significantly lower similarity among the sampling areas in summer and a higher proportion of carnivorous taxa in autumn. The findings suggested that long-term disturbance can lead to the dominance of smaller body-sized benthic species and reduced sediment quality, impeding ecological recovery of benthic organisms under such harsh environment.

Bioassessment of environmental quality based on taxonomic and functional traits of marine nematodes in the Bohai Sea, China

Free-living marine nematodes are valuable biological indicators for different environmental disturbances. Their taxonomic composition and functional traits often respond to environmental changes. In this study, marine nematodes, collected from the Bohai sea on the northeastern coast of China in 2014, were investigated in terms of their taxonomic composition and functional traits. Furthermore, the environmental quality of the investigated area was assessed based on nematode metrics. The studied nematode community showed spatial variation in taxonomic and functional composition, in response to changes in environmental variables such as sediment chlorophyll-a, phaeophytin-a, organic matter content, silt-clay content etc. Overall, high percentage of tolerant marine nematodes species or colonizers predominated, suggesting a disturbed environmental condition of the study area. Further results from the environmental quality assessment based on nematode metrics indicated a moderate quality status at the most investigated stations.

Zeta diversity patterns in metabarcoded lotic algal assemblages as a tool for bioassessment

Assessments of the ecological health of algal assemblages in streams typically focus on measures of their local diversity and classify individuals by morphotaxonomy. Such assemblages are often connected through various ecological processes, such as dispersal, and may be more accurately assessed as components of regional-, rather than local-scale assemblages. With recent declines in the costs of sequencing and computation, it has also become increasingly feasible to use metabarcoding to more accurately classify algal species and perform regional-scale bioassessments. Recently, zeta diversity has been explored as a novel method of constructing regional bioassessments for groups of streams. Here, we model the use of zeta diversity to investigate whether stream health can be determined by the landscape diversity of algal assemblages. We also compare the use of DNA metabarcoding and morphotaxonomy classifications in these zeta diversity-based bioassessments of regional stream health. From 96 stream samples in California, we used various orders of zeta diversity to construct models of biotic integrity for multiple assemblages of diatoms, as well as hybrid assemblages of diatoms in combination with soft-bodied algae, using taxonomy data generated with both DNA sequencing as well as traditional morphotaxonomic approaches. We compared our ability to evaluate the ecological health of streams with the performance of multiple algal indices of biological condition. Our zeta diversity-based models of regional biotic integrity were more strongly correlated with existing indices for algal assemblages classified using metabarcoding compared to morphotaxonomy. Metabarcoding for diatoms and hybrid algal assemblages involved rbcL and 18S V9 primers, respectively. Importantly, we also found that these algal assemblages, independent of the classification method, are more likely to be assembled under a process of niche differentiation rather than stochastically. Taken together, these results suggest the potential for zeta diversity patterns of algal assemblages classified using metabarcoding to inform stream bioassessments.

Pollution has negative effects on macrozoobenthic trait diversity in a large subtropical estuary

Changes in species composition and relative abundance caused by pollution might have an impact on the community dynamics and ecosystem functioning. Macrobenthos are widely used as indicators of marine environmental health due to their sensitive to disturbance. The present study aims to evaluate spatial and temporal variability of functional diversity of macrobenthos of the Montevideo and Canelones coastal zone along a pre-established pollution gradient, based on Biological Traits Analysis, and functional diversity indices. Body-size", "Feeding-mode", "Habitat", and "Indicator-role" were useful proxies to detect changes in environmental conditions in organically enriched habitats. FRic, FEve and FDis detected temporal variations but only FRic registered spatial variations. Differences among surveys would mainly reflect environmental variability caused by the 2009-2010 El Niño-Southern Oscillation event. Finally, negative correlations between FEve and FDis with AMBI suggest both indices as useful proxies of benthic environmental health, with potential to be used in monitoring and quality assessment programs.

Species and functional diversity of marine macrobenthic community and benthic habitat quality assessment in semi-enclosed waters upon recovering from eutrophication, Bohai Bay, China

This study investigated the structure and function of macrobenthic community in Bohai Bay upon improvement of water quality due to pollution abatement. A total of 166 species were collected in the summer and autumn sampling, with an increase in sensitive species recorded as compared to data from previous studies. While historical variations in species richness indicated signs of improvement in community structure, results of functional diversity indices revealed that the macrobenthic community in Bohai Bay was still in an early stage of recovery. From BIO-ENV analysis, habitat instability may hinder how community responded to water quality improvement. Results of the benthic habitat quality assessment also indicated that the ecological status in most areas of Bohai Bay was classified as good, while a few estuarine regions were categorized in a poor status.