Reorganization of bird communities along a rainforest elevation gradient during a strong El Niño event in Papua New Guinea.

The El Niño 2015 event, most extreme since 1997, led to severe droughts in tropical wet Papua New Guinea (PNG), reducing May to October dry season rainfall by 75% in the lowlands and 25% in the highlands. Such droughts are likely to have significant effects on terrestrial ecosystems, but they have been poorly explored in Papua New Guinea. Here, we report changes in bird community composition prior to, during, and after the 2015 El Niño event along the elevational gradient ranging from 200 m to 2700 m a.s.l. at the Mt. Wilhelm rainforest in PNG. The abundance of birds in the lowlands dropped by 60% but increased by 40% at elevations above 1700 m during El Niño year. In the following year, the individual bird species reached mean population sizes similar to pre-El Niño years but did not fully recover. Species richness roughly followed the pattern of observed abundance and quickly and fully re-established after the event to the pre- El Niño values. Thus, at least some terrestrial birds seem to react quickly to the extreme droughts in lowlands and shift to less affected mountain habitats. We recorded upper elevational range limits to shifts by more than 500 m a.s.l. in 22 bird species (out of 237 recorded in total) during El Niño year, in contrast to their typical ranges. Our study suggests that a strong El Niño event can have strong but reversible effects on bird communities as long as they have an opportunity to move to more favorable sites through undisturbed habitats.

Climate change affects the distribution of diversity across marine food webs.

Many studies predict shifts in species distributions and community size composition in response to climate change, yet few have demonstrated how these changes will be distributed across marine food webs. We use Bayesian Additive Regression Trees to model how climate change will affect the habitat suitability of marine fish species across a range of body sizes and belonging to different feeding guilds, each with different habitat and feeding requirements in the northeast Atlantic shelf seas. Contrasting effects of climate change are predicted for feeding guilds, with spatially extensive decreases in the species richness of consumers lower in the food web (planktivores) but increases for those higher up (piscivores). Changing spatial patterns in predator-prey mass ratios and fish species size composition are also predicted for feeding guilds and across the fish assemblage. In combination, these changes could influence nutrient uptake and transformation, transfer efficiency and food web stability, and thus profoundly alter ecosystem structure and functioning.

Assessment of the biological water quality and response of freshwater macroinvertebrates to thermal stress in an Afrotropical warm spring.

Freshwater macroinvertebrates have been widely used as environmental stress indicators. However, information on their response to natural thermal stress is relatively scarce, particularly in the tropics. Using the multimetric macroinvertebrate approach, the biological water quality of the warm and cold springs of the Ikogosi Warm Spring in Nigeria was evaluated, with a view to ascertaining the response of freshwater macroinvertebrates to natural thermal stress. Macroinvertebrates and water samples were collected from the warm (stressed) and cold (less-stressed) springs, as well as the confluence stream, within the renowned Ikogosi Warm Spring of Southwest Nigeria. The less-stressed cold spring had much more dissolved oxygen than the warm spring and other thermally stressed stations but less than the warm spring and other thermally stressed stations for water temperature, electrical conductivity, total dissolved solids, Ca2+, Mg2+, and water hardness. Generally, the macroinvertebrate taxonomic richness (30 species) and EPT richness (3 species) of the Ikogosi Warm Spring indicated an impaired freshwater system. Using the multimetric macroinvertebrate index (MMI), the warm spring was of poor biological water quality while the cold spring was of good biological water quality. At the confluence of both springs, the MMI declined to poor and moderate water quality. Although the thermal stress of the Ikogosi Warm Spring is natural, the government should take the necessary steps to regulate tourist activities so that the site's naturalness is preserved and the water quality is not further degraded on account of human-induced stressors such as deforestation, waste dumping, and washing activities.

The Impact of Lantana camara on Invertebrates and Plant Species of the Groenkloof Nature Reserve, South Africa.

Invasive plant species have negative ecological impacts such as displacing indigenous plants and invertebrates. These invasive plant species affect biodiversity by impacting indigenous vegetation and the food webs associated with this vegetation. We assessed how Lantana camara affects indigenous plant species richness and invertebrates and their feeding guilds in riparian habitats inside the Groenkloof Nature Reserve in South Africa. We showed: (1) A lower abundance and morphospecies richness of invertebrates as well as lower numbers of plant species in lantana-invaded habitat as compared to indigenous bush and grass-dominated habitats. (2) A Negative association between plant species richness and L. camara above ground mass and shoot density, but no association was found between plant species richness and the size of L. camara invaded areas. This finding suggests a link between the reduction in overall invertebrate abundance and morphospecies richness and the replacement of native plant species by invasive lantana. (3). This increased biomass in natural vegetation was even more evident for detrivores as compared to other feeding guilds. Extensive invasion by L. camara is affecting the quality of riparian ecosystems especially for invertebrates that rely on decaying plants and animals as food and this will affect overall biodiversity.

Elevational changes in insect herbivory on woody plants in six mountain ranges of temperate Eurasia: Sources of variation.

Current theory predicts that the intensity of biotic interactions, particularly herbivory, decreases with increasing latitude and elevation. However, recent studies have revealed substantial variation in both the latitudinal and elevational patterns of herbivory. This variation is often attributed to differences in study design and the type of data collected by different researchers. Here, we used a similar sampling protocol along elevational gradients in six mountain ranges, located at different latitudes within temperate Eurasia, to uncover the sources of variation in elevational patterns in insect herbivory on woody plant leaves. We discovered a considerable variation in elevational patterns among different mountain ranges; nevertheless, herbivory generally decreased with increasing elevation at both the community-wide and individual plant species levels. This decrease was mostly due to openly living defoliators, whereas no significant association was detected between herbivory and elevation among insects living within plant tissues (i.e., miners and gallers). The elevational decrease in herbivory was significant for deciduous plants but not for evergreen plants, and for tall plants but not for low-stature plants. The community-wide herbivory increased with increases in both specific leaf area and leaf size. The strength of the negative correlation between herbivory and elevation increased from lower to higher latitudes. We conclude that despite the predicted overall decrease with elevation, elevational gradients in herbivory demonstrate considerable variation, and this variation is mostly associated with herbivore feeding habits, some plant traits, and latitude of the mountain range.

Benthic polychaete community structure in the Yellow Sea Bottom Cold Water zone (YSBCW): Species diversity, temporal-spatial distribution, and feeding guilds.

The Yellow Sea Bottom Cold Water zone (YSBCW) is a unique seasonal phenomenon in the Yellow Sea, where sea-floor cold water formed in winter is maintained until summer. This survey was conducted at 36 sites from 2018 to 2020. We identified 130 species of polychaetes, with an average density of 275 individuals/m2. The number of species and density were different outside and inside of the YSBCW, and the outside was generally high. The remaining dominant species were all deposit feeders, although differences were observed in the surface or subsurface (burrowers). Correlations between polychaete community and environmental variables strongly correlated with depth, temperature, gravel, and sand. This study investigated polychaete community distribution, environmental characteristics, and feeding guilds in the YSBCW and can be used as a basic database for comprehensive research related to the Yellow Sea in the future.

Ecological signal in the size and shape of marine amniote teeth.

Amniotes have been a major component of marine trophic chains from the beginning of the Triassic to present day, with hundreds of species. However, inferences of their (palaeo)ecology have mostly been qualitative, making it difficult to track how dietary niches have changed through time and across clades. Here, we tackle this issue by applying a novel geometric morphometric protocol to three-dimensional models of tooth crowns across a wide range of raptorial marine amniotes. Our results highlight the phenomenon of dental simplification and widespread convergence in marine amniotes, limiting the range of tooth crown morphologies. Importantly, we quantitatively demonstrate that tooth crown shape and size are strongly associated with diet, whereas crown surface complexity is not. The maximal range of tooth shapes in both mammals and reptiles is seen in medium-sized taxa; large crowns are simple and restricted to a fraction of the morphospace. We recognize four principal raptorial guilds within toothed marine amniotes (durophages, generalists, flesh cutters and flesh piercers). Moreover, even though all these feeding guilds have been convergently colonized over the last 200 Myr, a series of dental morphologies are unique to the Mesozoic period, probably reflecting a distinct ecosystem structure.

Changes in Biomass and Diversity of Soil Macrofauna along a Climatic Gradient in European Boreal Forests.

Latitudinal gradients allow insights into the factors that shape ecosystem structure and delimit ecosystem processes, particularly climate. We asked whether the biomass and diversity of soil macrofauna in boreal forests change systematically along a latitudinal gradient spanning from 60° N to 69° N. Invertebrates (3697 individuals) were extracted from 400 soil samples (20 × 20 cm, 30 cm depth) collected at ten sites in 2015-2016 and then weighed and identified. We discovered 265 species living in soil and on the soil surface; their average density was 0.486 g d·w·m-2. The species-level diversity decreased from low to high latitudes. The biomass of soil macrofauna showed no latitudinal changes in early summer but decreased towards the north in late summer. This variation among study sites was associated with the decrease in mean annual temperature by ca 5 °C and with variation in fine root biomass. The biomass of herbivores and fungivores decreased towards the north, whereas the biomass of detritivores and predators showed no significant latitudinal changes. This variation in latitudinal biomass patterns among the soil macrofauna feeding guilds suggests that these guilds may respond differently to climate change, with poorly understood consequences for ecosystem structure and functions.

Patterns of morphological traits shaping the feeding guilds in the intertidal mudflat fishes of the Indian Sundarbans.

Broad-scale patterns of resource utilization and the corresponding morphological evolution is a result of an integral relationship among form and function. In addition, there is also an inherent role of the latter in determining species co-interaction and assemblage pattern that forms an integral aspect of ecological research. The present study aimed to evaluate the ecomorphological relationship among 37 fish species inhabiting the intertidal mudflats of the Indian Sundarbans by outlining the following objectives: (i) identifying and characterizing feeding guilds/groups and (ii) understanding the inter-relationship between morphometry with (a) the established feeding guild classifications and (b) observed prey taxa (that characterizes these feeding groups) for determining the role of morphometry in prey acquisition followed by (iii) the evaluation of their potential phylogenetic convergence among the species. For the first objective, two approaches for feeding guild classification were made (3-Guild and 8-Guild) for assessing the prediction accuracy of morphological characters in identifying the different guilds. While the former was based on troph values, the latter classification mode relied on the similarities in diet composition among the different fish species. For addressing the second objective, we employed two different models namely, linear discriminant (LDA) and redundancy analysis (RDA). While the LDA model tested the prediction accuracy of morphological traits in classifying the different feeding guilds, RDA was applied to model the correlation between the morphological traits and the prey categories. In the LDA model, morphological characters showed higher accuracy (78.4%) in classifying three feeding groups rather than eight feeding groups (73%). Following this, the RDA model (explaining 79.78% of constrained variance) showed gill raker intensity, protrusion length, head depth, caudal peduncle, eye diameter and inter-orbital distance to be highly associated with selection of specific prey types by species, thereby characterizing a particular feeding guild. However, generalized linear models testing for correlation between troph value and feeding groups showed substantial variation (90.35%) in the dietary index being explained by the 8-Guild classification. Hence, our study maintains the assumption that broad morphological differentiation acts as one of the underlying processes resulting in dietary variations that results in the varying modes of resource utilization by the coexisting species, thereby determining the structure of a trophic guild. Furthermore, it also suggests that in terms of prey abundance or selectivity, the 8-Guild model is much more conducive in representing the feeding habits of the species while the morphological traits reflected a relatively broader scheme of classification, (i.e., 3-Guild model) with certain traits being phylogenetically conserved within these groups.

Incorporation of feeding functional group information informs explanatory patterns of long-term population changes in fish assemblages.

The objective of this study was to evaluate long term trends of fish taxa in southern Lake Michigan while incorporating their functional roles to improve our understanding of ecosystem level changes that have occurred in the system over time. The approach used here highlighted the ease of incorporating ecological mechanisms into population models so researchers can take full advantage of available long-term ecosystem information. Long term studies of fish assemblages can be used to inform changes in community structure resulting from perturbations to aquatic systems and understanding these changes in fish assemblages can be better contextualized by grouping species according to functional groups that are grounded in niche theory. We hypothesized that describing the biological process based on partial pooling of information across functional groups would identify shifts in fish assemblages that coincide with major changes in the ecosystem (e.g., for this study, shifts in zooplankton abundance over time). Herein, we analyzed a long-term Lake Michigan fisheries dataset using a multi-species state space modeling approach within a Bayesian framework. Our results suggested the population growth rates of planktivores and benthic invertivores have been more variable than general invertivores over time and that trends in planktivores can be partially explained by ecosystem changes in zooplankton abundance. Additional work incorporating more ecosystem parameters (e.g., primary production, etc.) should be incorporated into future iterations of this novel modeling concept.

Microplastics in some fish species and their environs in Eastern Visayas, Philippines.

Microplastics are a global concern, and yet, Philippine studies about it are still wanting. This study investigated microplastic ingestion among detritus-feeding mullet versus the herbivorous rabbitfish, and between freshwater and marine fishes. The first part aimed to compare microplastics in fishes' guts differing in feeding guilds, individual sizes, and body weights. The second part compared MPs in fishes' guts and their surrounding waters. Part one revealed that herbivores (58.57%) ingested more MPs than their detritivore-counterparts (30.0%). Pearson correlation, averaging 0.06, suggests a weak correlation between fish weight and MPs amount for both species. Part two showed marine fishes (66.0%) ingested more MPs than its freshwater counterparts (45.0%). A very weak correlation was observed between fish weight and amount of MPs ingested. Fish along the estuary ingested more MPs than those in other stations. No significant differences (p = 0.23) between the MPs in the water samples from each sampling stations was found.

Does trait-based joint species distribution modelling reveal the signature of competition in stream macroinvertebrate communities?

The occupancy and abundance of species are jointly driven by local factors, such as environmental characteristics and biotic interactions, and regional-scale factors, such as dispersal and climate. Recently, it has been shown that biotic interactions shape species occupancies and abundances beyond local extents. However, for small ectothermic animals, particularly for those occurring in freshwater environments, the importance of biotic interactions remains understudied. Species-to-species associations from joint species distribution models (i.e. species associations while controlling for environmental characteristics) are increasingly used to draw hypotheses of which species possibly show biotic interactions. We studied whether species-to-species associations from joint species distribution models show signs of competition using a hypothesis testing framework in stream macroinvertebrate communities at regional extent. We sampled aquatic macroinvertebrates from 105 stream sites in western Finland encompassing a latitudinal gradient of c. 500 kilometres. We hypothesized that if competition drives these associations (H1) functionally, similar species are mostly negatively associated, whereas functionally dissimilar species show random associations. We further hypothesized that the relationship between functional dissimilarity and the strength of association is more pronounced (H2) for abundances rather than occupancies, (H3) at small grain (i.e. stream site) rather than at large grain (i.e. river basin), and (H4) among species having weak dispersal ability than among species with high dispersal ability. Stream macroinvertebrates showed both negative and positive species-to-species associations while controlling for habitat characteristics. However, the negative associations were mostly at large grain (river basin) rather than at small grain (stream site), in occupancy rather than abundance, and not related to species functional dissimilarity or to their dispersal ability. Thus, all our hypotheses considering possible competition (H1-H4) were rejected. Competition does not appear to be a major driving force of stream macroinvertebrate communities at the spatial grain sizes considered. The observed positive associations in occupancy at small grain (stream site) may be attributed to species' similar microhabitat preferences, whereas at large grain (river basin), they may stem from metacommunity dynamics. Our results highlight that species traits were necessary to interpret whether or not species-to-species associations from joint species distribution models resulted from biotic interactions.

Mayfly response to different stress types in small and mid-sized lowland rivers.

Freshwater ecosystems are endangered worldwide by various human pressures, resulting in dramatic habitat and species loss. Many aquatic invertebrates respond to disturbances in their habitat, and mayflies are among the most sensitive ones. Therefore, we investigated mayfly response to anthropogenic disturbances at 46 study sites encompassing slightly to heavily modified small and mid-sized lowland streams and rivers. Mayfly nymphs were sampled between April and September 2016 using a benthos hand net. A total of 21 species was recorded, with Cloeon dipterum (Linnaeus, 1761) being the most frequently recorded one. Nevertheless, the taxa richness was rather low per site, i.e., between zero and nine. Assemblage structure had a high share of lower reaches and lentic (potamic and littoral) elements, and detritivores (gatherers/collectors and active filter feeders). This indicates that hydromorphological alterations lead to assemblage "potamisation" in small and mid-sized rivers. More mayfly species were related to higher oxygen concentration and lower water temperature, abundance of aquatic vegetation and total organic carbon. Additionally, the assemblage diversity and abundance were negatively associated with increasing intensive agriculture area at the catchment scale. This study confirms mayfly bio-indicative properties, i.e., their sensitivity to alterations of their habitat and pollution, but also provides new data related to mayfly response to the impacted environment. Those data can be used for management and protection activities of lowland rivers and their biota according to the requirements of the European Water Framework Directive.

Biomass, abundances, and abundance and geographical range size relationship of birds along a rainforest elevational gradient in Papua New Guinea.

The usually positive inter-specific relationship between geographical range size and the abundance of local bird populations comes with exceptions. On continents, the majority of these exceptions have been described from tropical montane areas in Africa, where geographically-restricted bird species are unusually abundant. We asked how the local abundances of passerine and non-passerine bird species along an elevational gradient on Mt. Wilhelm, Papua New Guinea relate to their geographical range size. We collected data on bird assemblages at eight elevations (200-3,700 m, at 500 m elevational increments). We used a standardized point-counts at 16 points at each elevational study site. We partitioned the birds into feeding guilds, and we obtained data on geographical range sizes from the Bird-Life International data zone. We observed a positive relationship between abundance and geographical range size in the lowlands. This trend changed to a negative one towards higher elevations. The total abundances of the assemblage showed a hump-shaped pattern along the elevational gradient, with passerine birds, namely passerine insectivores, driving the observed pattern. In contrast to abundances, the mean biomass of the bird assemblages decreased with increasing elevation. Our results show that montane bird species maintain dense populations which compensate for the decreased available area near the top of the mountain.

Levels and distribution pattern of organochlorine pesticide residues in eggs of 22 terrestrial birds from Tamil Nadu, India.

Long-term monitoring is essential to assess the patterns and distribution of the residues of organochlorine pesticides (OCPs) in biota. Bird eggs have several advantages than other environmental matrixes, which have been used extensively to portray the accumulation and distribution of OCPs. The present study investigated the organochlorine pesticide (OCP) residues in eggs of 22 species of terrestrial birds collected from Tamil Nadu, India. Eggs found abandoned were collected during nest monitoring between 2001 and 2008 and analyzed for the presence of organochlorine pesticide residues. The results showed that the mean concentrations of total hexachlorohexane (∑HCHs), total dichlorodiphenyltrichloroethane (∑DDTs), heptachlor epoxide, and dieldrin ranged from non-detectable (nd) to 2800 ng/g, nd to1000 ng/g, nd to 700 ng/g, and nd to 240 ng/g on a wet mass (wm) basis, respectively. The variation in magnitude of contamination among the species and feeding guilds were not significantly different (p > 0.05). Among the OCPs analyzed, the residues of ß-HCH and p,p'-DDE were found to be the abundant in concentration. Similarly, among various bird species studied, the highest concentrations of ∑OCPs (> 5000 ng/g wm) were recorded in the eggs of gray junglefowl, scaly-breasted munia, and red-whiskered bulbul. This may be due to their widespread occurrence of their habitat at proximity to the agricultural fields, where organochlorines were in use until recently. Among the various contaminants analyzed, concentrations of p,p'-DDE and heptachlor epoxide exceeded the threshold levels of toxicity for wild birds in > 5% of the egg samples. Hence, this study indicates the need for continued monitoring and further systematic ecotoxicological investigation of these compounds not only in eggs but also in other environmental media.

Disentangling the effects of plant species invasion and urban development on arthropod community composition.

Urban development and species invasion are two major global threats to biodiversity. These threats often co-occur, as developed areas are more prone to species invasion. However, few empirical studies have tested if both factors affect biodiversity in similar ways. Here we study the individual and combined effects of urban development and plant invasion on the composition of arthropod communities. We assessed 36 paired invaded and non-invaded sample plots, invaded by the plant Antigonon leptopus, with half of these pairs located in natural and the other half in developed land-use types on the Caribbean island of St. Eustatius. We used several taxonomic and functional variables to describe community composition and diversity. Our results show that both urban development and A. leptopus invasion affected community composition, albeit in different ways. Development significantly increased species richness and exponential Shannon diversity, while invasion had no effect on these variables. However, invasion significantly increased arthropod abundance and caused biotic homogenization. Specifically, uninvaded arthropod communities were distinctly different in species composition between developed and natural sites, while they became undistinguishable after A. leptopus invasion. Moreover, functional variables were significantly affected by species invasion, but not by urban development. Invaded communities had higher community-weighted mean body size and the feeding guild composition of invaded arthropod communities was characterized by the exceptional numbers of nectarivores, herbivores, and detritivores. With the exception of species richness and exponential Shannon diversity, invasion influenced four out of six response variables to a greater degree than urban development did. Hence, we can conclude that species invasion is not just a passenger of urban development but also a driver of change.

Plant phylogeny drives arboreal caterpillar assemblages across the Holarctic.

Assemblages of insect herbivores are structured by plant traits such as nutrient content, secondary metabolites, physical traits, and phenology. Many of these traits are phylogenetically conserved, implying a decrease in trait similarity with increasing phylogenetic distance of the host plant taxa. Thus, a metric of phylogenetic distances and relationships can be considered a proxy for phylogenetically conserved plant traits and used to predict variation in herbivorous insect assemblages among co-occurring plant species.Using a Holarctic dataset of exposed-feeding and shelter-building caterpillars, we aimed at showing how phylogenetic relationships among host plants explain compositional changes and characteristics of herbivore assemblages.Our plant-caterpillar network data derived from plot-based samplings at three different continents included >28,000 individual caterpillar-plant interactions. We tested whether increasing phylogenetic distance of the host plants leads to a decrease in caterpillar assemblage overlap. We further investigated to what degree phylogenetic isolation of a host tree species within the local community explains abundance, density, richness, and mean specialization of its associated caterpillar assemblage.The overlap of caterpillar assemblages decreased with increasing phylogenetic distance among the host tree species. Phylogenetic isolation of a host plant within the local plant community was correlated with lower richness and mean specialization of the associated caterpillar assemblages. Phylogenetic isolation had no effect on caterpillar abundance or density. The effects of plant phylogeny were consistent across exposed-feeding and shelter-building caterpillars.Our study reveals that distance metrics obtained from host plant phylogeny are useful predictors to explain compositional turnover among hosts and host-specific variations in richness and mean specialization of associated insect herbivore assemblages in temperate broadleaf forests. As phylogenetic information of plant communities is becoming increasingly available, further large-scale studies are needed to investigate to what degree plant phylogeny structures herbivore assemblages in other biomes and ecosystems.

Vertical stratification of a temperate forest caterpillar community in eastern North America.

Vertical niche partitioning might be one of the main driving forces explaining the high diversity of forest ecosystems. However, the forest's vertical dimension has received limited investigation, especially in temperate forests. Thus, our knowledge about how communities are vertically structured remains limited for temperate forest ecosystems. In this study, we investigated the vertical structuring of an arboreal caterpillar community in a temperate deciduous forest of eastern North America. Within a 0.2-ha forest stand, all deciduous trees ≥ 5 cm diameter at breast height (DBH) were felled and systematically searched for caterpillars. Sampled caterpillars were assigned to a specific stratum (i.e. understory, midstory, or canopy) depending on their vertical position and classified into feeding guild as either exposed feeders or shelter builders (i.e. leaf rollers, leaf tiers, webbers). In total, 3892 caterpillars representing 215 species of butterflies and moths were collected and identified. While stratum had no effect on caterpillar density, feeding guild composition changed significantly with shelter-building caterpillars becoming the dominant guild in the canopy. Species richness and diversity were found to be highest in the understory and midstory and declined strongly in the canopy. Family and species composition changed significantly among the strata; understory and canopy showed the lowest similarity. Food web analyses further revealed an increasing network specialization towards the canopy, caused by an increase in specialization of the caterpillar community. In summary, our study revealed a pronounced stratification of a temperate forest caterpillar community, unveiling a distinctly different assemblage of caterpillars dwelling in the canopy stratum.

Effects of fish cage culture and suspended oyster culture on macrobenthic communities in Xiangshan Bay, a semi-enclosed subtropical bay in eastern China.

The impacts of fish cage culture and suspended oyster culture on macrobenthic communities were investigated in Xiangshan Bay, China, on a seasonal basis from January to October of 2015. Samples were collected from a fish cage farm, a suspended oyster farm, and two corresponding reference sites. Two-way ANOVA results showed that species richness, abundance, biomass, and Shannon-Wiener diversity differed significantly between the four different investigated areas, and different seasons as well. Cluster analysis showed that macrobenthic community composition in the fish and oyster culture areas significantly differed from that in the reference sites, respectively. Trophic structure of macrobenthos in the fish and oyster culture areas mostly clustered together owing to higher abundance and biomass of surface-deposit feeders and carnivores. The macrobenthic communities and feeding guilds correlated highly with environmental factors, such as bottom water chlorophyll a and nutrients, as well as sediment total organic carbon. Although integrated multi-trophic aquaculture is regarded as a suitable approach to coordinate desirable economic, social, and environmentally sustainable outcomes, coastal ecosystems may suffer from large-scale nutrient enrichment due to aquaculture and other human activities, which should not be considered in isolation.

Spatio-temporal variability in macrobenthic communities and trophic structure of a tropical estuary and its adjacent coastal waters.

Spatio-temporal distribution of the macrobenthic community (> 500 µm) and the trophic ecology of polychaetes were studied for a year in the Cochin estuary (CE) and its adjacent coastal waters. A profound influence of the southwest monsoon (SWM) was evident in the CE, a tropical monsoonal estuary, during the present study. The sediment texture and macrobenthic density exhibited a pronounced spatial variation in the estuary, while in the coastal waters temporal changes were more prominent. Polychaetes formed the dominant taxa in terms of density and diversity in the estuary (53 species belonging to 25 families) as well as in the adjacent coastal waters (39 species belonging to 20 families). The polychaete species Diopatra neapolitana dominated during nonmonsoonal periods was found to be replaced by the higher abundance of Pisione sp. in the CE during the monsoon period. On the other hand, in the coastal waters, Cossura coasta, the dominant species during the pre-monsoon period, was replaced by the surface deposit feeder Paraprionospio pinnata during the monsoon and post-monsoon periods. The study evidenced the combined influence of sediment texture, salinity, and food availability in determining the distribution and abundance of the macrobenthic fauna in the CE and adjacent coastal waters. Feeding guild analysis and trophic importance index showed that carnivores and surface and subsurface deposit feeders were the dominant and trophically important feeding guilds in the study area. Redundancy analysis showed that the sandy substratum supported a diversified functional composition in the estuary and its adjacent coastal waters, and motile, discretely motile polychaetes and filter feeders were more associated with the sandy substratum. Results of the present study revealed that the seasonally fluctuating polychaete community structure in the study area was predominantly controlled by their diversified feeding habits and the ecological descriptors of the polychaete feeding guilds were linked primarily to the substratum type and food availability.