Coastal Benthic Communities Research Articles

Embedded Complexity of Evolutionary Sequences.

Multiple pathways and outcomes are common in evolutionary sequences for biological and other environmental systems due to nonlinear complexity, historical contingency, and disturbances. From any starting point, multiple evolutionary pathways are possible. From an endpoint or observed state, multiple possibilities exist for the sequence of events that created it. However, for any observed historical sequence-e.g., ecological or soil chronosequences, stratigraphic records, or lineages-only one historical sequence actually occurred. Here, a measure of the embedded complexity of historical sequences based on algebraic graph theory is introduced. Sequences are represented as system states S(t), such that S(t - 1) ≠ S(t) ≠ S(t + 1). Each sequence of N states contains nested subgraph sequences of length 2, 3, …, N - 1. The embedded complexity index (which can also be interpreted in terms of embedded information) compares the complexity (based on the spectral radius λ1) of the entire sequence to the cumulative complexity of the constituent subsequences. The spectral radius is closely linked to graph entropy, so the index also reflects information in the sequence. The analysis is also applied to ecological state-and-transition models (STM), which represent observed transitions, along with information on their causes or triggers. As historical sequences are lengthened (by the passage of time and additional transitions or by improved resolutions or new observations of historical changes), the overall complexity asymptotically approaches λ1 = 2, while the embedded complexity increases as N2.6. Four case studies are presented, representing coastal benthic community shifts determined from biostratigraphy, ecological succession on glacial forelands, vegetation community changes in longleaf pine woodlands, and habitat changes in a delta.

Shifts in dominance of benthic communities along a gradient of water temperature and turbidity in tropical coastal ecosystems.

Tropical coastal benthic communities will change in species composition and relative dominance due to global (e.g., increasing water temperature) and local (e.g., increasing terrestrial influence due to land-based activity) stressors. This study aimed to gain insight into possible trajectories of coastal benthic assemblages in Raja Ampat, Indonesia, by studying coral reefs at varying distances from human activities and marine lakes with high turbidity in three temperature categories (<31°C, 31-32°C, and >32°C). The benthic community diversity and relative coverage of major benthic groups were quantified via replicate photo transects. The composition of benthic assemblages varied significantly among the reef and marine lake habitats. The marine lakes <31°C contained hard coral, crustose coralline algae (CCA), and turf algae with coverages similar to those found in the coral reefs (17.4-18.8% hard coral, 3.5-26.3% CCA, and 15-15.5% turf algae, respectively), while the higher temperature marine lakes (31-32°C and >32°C) did not harbor hard coral or CCA. Benthic composition in the reefs was significantly influenced by geographic distance among sites but not by human activity or depth. Benthic composition in the marine lakes appeared to be structured by temperature, salinity, and degree of connection to the adjacent sea. Our results suggest that beyond a certain temperature (>31°C), benthic communities shift away from coral dominance, but new outcomes of assemblages can be highly distinct, with a possible varied dominance of macroalgae, benthic cyanobacterial mats, or filter feeders such as bivalves and tubeworms. This study illustrates the possible use of marine lake model systems to gain insight into shifts in the benthic community structure of tropical coastal ecosystems if hard corals are no longer dominant.

Environmental impact on marginal coastal benthic communities within the Jeju Island, South Korea temperate transition zone

Aim of studyMarine climatic transition zones are boundary areas of major climate zones, here the boundary between the subtropical and temperate zones. They present areas containing high abundance of organisms living at the limit of their physiological tolerance. These marginal populations are particularly sensitive to changes in their environment. As such, marine climatic transition zones are excellent natural playgrounds for climate change-related hypothesis testing, especially with respect to marine habitat response to ocean warming. The marginal biogenic habitats around Jeju Island, South Korea, which lies within the temperate transition zone, have gradually changed from macroalgal-dominated to hard coral-dominated habitats. Understanding the specific abiotic environmental factors that influence the distribution of the marginal populations in temperate transition zones (i.e., species at their occurrence limit) is crucial to predicting and managing temperate zone habitat changes caused by climate change. This study aims to identify the specific abiotic environmental factors that contribute to explaining the current spatial distribution of the declining temperate and expanding subtropical foundation species in Jeju waters.MethodsCoverage and composition of sessile benthic communities were determined by photo-quadrat analysis at two depths (10 m and 15 m) at three sites along the island’s south, east, and north coasts in May and November 2022. Divergences in community composition between sites were characterized in light of ten quantitative environmental parameters.ResultsOur results show that sessile foundation communities vary significantly at different sites around the island. While the south is defined by high-latitude hard corals, predominately Alveopora japonica, the east is defined by the temperate canopy-forming macroalga Ecklonia cava, and the north is characterized by coralline algae. Winter sea surface temperature, water transparency, nutrient concentration, and water movement were statistically the most impactful environmental factors determining which foundation species constitute each distinct benthic community.ConclusionThis study provides valuable baseline information on the impacts of abiotic environmental factors on marine sessile communities in a temperate transition zone.

Effects of micro‐ and nanoplastics on the physiology and metabolism of Portunus trituberculatus

AbstractPortunus trituberculatus is important in coastal benthic communities and a favorite seafood for coastal residents. However, microplastics have been detected in different tissues of P. trituberculatus, but the toxicological effects of micro‐ and nanoplastics (MNPs) on the different tissues of P. trituberculatus have not been reported. We found that the lethal effect of MNPs on P. trituberculatus is not obvious, but they can stimulate the body's stress response. The responses of P. trituberculatus tissues to MNPs are different, which may be due to differences in enzyme reactions between tissues and organs. Compared with microplastics (MPs), nanoplastics (NPs) have a more significant physiological and metabolic stress effect on P. trituberculatus because of their smaller particle size. In summary, plastic particles have physiological stress effects on the physiological metabolism of P. trituberculatus, which may be closely related to the plastic's particle size and concentration.

Insight on thermal stress response of demosponge Chondrosia reniformis (Nardo, 1847)

Global warming has led to an increase in extreme weather and climate phenomena, including floods and heatwaves. Marine heatwaves have frightening consequences for coastal benthic communities around the world. Each species exhibits a natural range of thermal tolerance and responds to temperature variations through behavioral, physiological, biochemical, and molecular adjustments. Physiological stress leading to disease and mass mortality appears when tolerance thresholds are exceeded. Sessile species are therefore particularly affected by these phenomena. Among these sessile species, marine sponges are important members of coral reef ecosystems. To better understand the sponge thermal stress response, we tested the response of demosponge Chondrosia reniformis (Nardo, 1847) to three different temperatures (8 °C, 24 °C and 30 °C) during two exposure periods of time (4 and 14 h). Histological studies of whole parts of the sponge, biochemical analyses (Defense enzymes) and gene expression levels of some target genes were undertaken in this study. The exposure to cold temperature (8 °C) resulted in inhibition of antioxidant enzymes and less modification in the gene expression level of the heat shock proteins (HSPs). These latter were strongly upregulated after exposure to a temperature of 24 °C for 4 h. However, exposure to 30 °C at both periods of time resulted in indication of HSP, antioxidant enzymes, the gene involved in the apoptosis process (Bcl-2: B-cell lymphoma 2), the gene involved in inflammation (TNF: Tumor Necrosis Factor), as well as the aquaporin gene, involved in H2O2 permeation. Moreover, the normal organization of the whole organism was disrupted by the extension and fusion of choanocyte chambers and alteration of the pinacoderm. Interestingly, exposure to sublethal temperatures may show that this sponge has an adaptation threshold temperature. These insights into the adaptation mechanisms of sponges contribute to better management and conservation of sponges and to the prediction of ecosystem trajectories with future climate change.

Influence of sea-ice dynamics on coastal Antarctic benthos: A case study on lantern clams (Laternula elliptica) in Adélie Land

Polar regions are warming faster than the world average and are profoundly affected by changes in the spatio-temporal dynamics of sea ice, with largely unknown repercussions on the functioning of marine ecosystems. Here, we investigated the impacts of interannual sea-ice variability on coastal benthic communities in Antarctica, focusing on a close-to-pristine area (Adélie Land). We investigated shell growth of the circum-Antarctic bivalve Laternula elliptica, considered a key species in these soft bottom benthic communities. Chondrophores of live-collected clams were prepared using standard sclerochronological methods to study the interannual variability of shell growth from 1996 to 2015. Our results show that the master chronology varied with sea-ice dynamics. When sea ice breaks up too early, sympagic algae do not have time to accumulate sufficiently high biomass, thus strongly limiting the energy input to the benthos. This negatively affects the physiological performance of L. elliptica, thereby altering their population dynamics and hence the functioning of these soft-bottom ecosystems.

Diet and Feeding Ecology of the Whitespotted Eagle Ray (Aetobatus narinari) from Florida Coastal Waters Revealed via DNA Barcoding

The whitespotted eagle ray (Aetobatus narinari) is a highly mobile, predatory batoid distributed throughout shallow, warm–temperate to tropical Atlantic Basin waters from North Carolina to Brazil. The species’ strong, plate-like dentition facilitates the consumption of hard-shelled prey, and due to effective winnowing behavior, it is a significant challenge to identify prey based on soft tissues alone. Here, we report on the first analysis of whitespotted eagle ray diet in Florida waters using visual-based gut content analysis complemented with DNA barcoding. Gut contents were obtained via gastric lavage from 50 individuals collected in the Indian River Lagoon and off Sarasota, Florida. Of the 211 unique prey samples collected, 167 were deemed suitable for sequencing. Approximately 56.3% of samples yielded positive species matches in genetic databases. Results from the sequenced data indicate that the whitespotted eagle ray diet in Florida is mainly comprised of bivalves and gastropods, with variable inclusion of crustaceans. Despite positive identification of venerid clams, there was no evidence for the consumption of hard clams (Mercenaria spp.), a major shellfish aquaculture and restoration species in Florida. Such wide-ranging prey species from various trophic guilds and locations highlight the whitespotted eagle ray’s diverse role in the top-down regulation of coastal benthic communities.

Spatial and temporal changes of subtidal benthic communities in Antofagasta Bay (SE Pacific) stressed by permanent human disturbances

Human activities have impacted the coastal area of Antofagasta Bay for decades, particularly miners’ activities (loading of mineral concentrates of Cu, Zn, Pb, and Mg), port operations, tourism, desalination plants, artisanal fishing, and sewage discharge. Subtidal coastal benthic communities were assessed in 7 sectors with different magnitudes of anthropogenic disturbances between the years 2008 to 2011 at Antofagasta Bay. Transennella pannosa, Incatella cingulata, Crassilabrum crassilabrum, and Leukoma thaca dominated the communities in all years of study. Based on the type of feeding behavior, the highest biomass was evidenced for the suspensivore group in all years of study, followed by the carnivore species. The highest average richness and average Shannon diversity were observed in sectors with medium and high levels of disturbances. In contrast, the highest average species dominance was registered in a sector with low disturbances. Community structure differed significantly between the seven sectors over the four years. The analysis of classification and ordination showed the conformation of three groups of sectors based on their dissimilarities. The differences were best explained by the sectors with low and high disturbances and by the presence of bivalves, ascidians, gastropods, and algae. It was demonstrated that the reduction or absence of fishing pressure could explain species’ high richness and diversity. Likewise, the sectors under low disturbance pressure showed the highest biomass and dominance of species. The information obtained in the current work could be used to design management strategies for conservation, monitoring, and restoration programs.

Faunistic and Structural Changes in Shallow Coastal Benthic Communities of the Ebre Delta (NW Mediterranean Sea)

The Ebre Delta (NW Mediterranean), which is considered a highly vulnerable ecosystem, is one of the most important European wetlands and belongs to the Natura 2000 network. The present study aims to characterize the benthic megainvertebrate communities inhabiting the Ebre Delta soft-bottom infralittoral to acquire faunistic and biological knowledge for two periods of time, 23 years apart. Experimental trawls were conducted during the two periods (1992–1993 and 2016–2017) in three depth strata, between 5 and 25 m. A total of 139 and 170 taxa were collected at each period, respectively. Our results showed that community species composition and structure varied between periods and among depth strata. Overall, a large decrease in density and biomass was detected for most species in all three depth strata examined (0–5, 15–20, and 20–25 m) in 2016–2017, especially in the shallowest stratum. Species richness was higher in 2016–2017 than in 1992–1993, and the lowest values were found at the shallowest stratum in both periods. The significant biomass losses herein reported highlight the need to increase, in time and effort, the monitoring of large marine invertebrates in coastal areas, where many taxa provide important ecosystem functions and services.

The interplay between terrestrial organic matter and benthic macrofauna: Framework, synthesis, and perspectives

AbstractEcosystems are shaped by physical, chemical, and biological drivers, which affect the quality and quantity of basal energy sources, with impacts that cascade to higher trophic levels. In coastal, shelf, and marine habitats, terrestrial‐derived organic matter (ter‐OM) can be a key driver of ecosystem structure and function. Climate change is expected to alter land–ocean connectivity in many regions, with a broad range of potential consequences for impacted ecosystems, particularly in the coastal zone. The benthic compartment is an important link between the large organic carbon pools stored on land and the marine environment. At the same time, the macrofauna plays a key role in the processing, biological uptake, and fate of ter‐OM in the aquatic environment, with implications for coastal ecosystem functioning, benthic–pelagic coupling, carbon burial, and biogeochemical cycles. However, information about relationships between land–ocean connectivity (including ter‐OM loads) and coastal benthic community responses remains spread across disciplines, and a broad perspective on the potential impacts of a changing climate is still missing. Here, we explore the interplay between benthic macrofaunal communities and ter‐OM through a paired narrative and research weaving analysis, which combines systematic mapping and bibliometric analysis. The review describes the past development and status of the research field as well as the lack of information in some geographical regions and habitats worldwide. We highlight the role of macrofauna in carbon cycling and the growing evidence that ter‐OM plays a key role in the structure and function of benthic communities, not strictly limited to estuarine habitats. Climate change poses challenges for the prediction of future ter‐OM fluxes and potential macrofauna responses to this additional stressor, thus requiring new methodological approaches (e.g., multimarker approaches for OM characterization) and long‐term monitoring programs across different habitats and spatiotemporal scales.

Climate change-related warming reduces thermal sensitivity and modifies metabolic activity of coastal benthic bacterial communities

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming.

Spatial and temporal dynamics of coastal benthic microbial communities along a salinity gradient

The Baltic Sea is a unique brackish water ecosystem that has been studied for decades; however, knowledge about the diversity of the benthic communities of bacteria and microbial eukaryotes within this system is sparse. Using an amplicon sequencing approach, we evaluated alpha and beta diversity of shallow-water coastal microbial sediment communities and their relationship to several environmental factors, on both a large spatial scale in the Baltic Sea and the adjacent North Sea, as well as on a temporal scale at selected sites along the salinity gradient in the Baltic Sea. We found salinity to be among the drivers of alpha diversity for bacteria but not for eukaryotes; however, community network structure appeared to change between sites of different salinity. Furthermore, beta diversity analyses revealed that communities in the poly- to mesohaline sections of the study area were affected to a higher degree by temperature, nutrient and sediment characteristics. This study shows that the structure of coastal microbial communities is to some degree related to salinity, but other factors also play a role.

Dominance of the scleractinian coral Alveopora japonica in the barren subtidal hard bottom of high-latitude Jeju Island off the south coast of Korea assessed by high-resolution underwater images.

Coastal benthic communities in temperate regions have been influenced by climate change, including increasing sea-surface temperature. Nevertheless, scleractinian coral Alveopora japonica Eguchi, 1968, is thriving in shallow subtidal hard bottoms around Jeju Island, off the southern coast of Korea. The presence of this corals has negatively impacted subtidal kelp populations in Jeju Island. However, there is no study to document how the presence or absence of this coral relates to other benthic communities. This study investigated the benthos in three shallow subtidal sites (Shinheung (SH), Bukchon (BC), and Seongsan (SS)) in northern Jeju using underwater photography. Macro-benthic organisms appearing on a 1 × 20 m line transect installed at depths of 5, 10, and 15 m at each site were analyzed. Results showed that of the three sites investigated, A. japonica colonies were most abundant at BC, accounting for 45.9% and 72.8% of the total transect area at 10 m and 15 m, respectively. At SS, A. japonica occupied 15.3% of the total area at 15 m and less than 1% at 5 m and 10 m. The same at SH accounted for 10% of the total area at 5 m, and less than 1% at 10 m and 15 m. Dead and bleached colonies accounted for 1.2-11.5% and 1.8-5.7%, respectively, at 5, 10, and 15 m at three sites. At SS, canopy-forming brown algae Ecklonia cava and Sargassum spp. accounted for 20.2 and 24.3% of the total transect area, respectively, at 5 m depth. In contrast, the percent cover of E. cava and Sargassum spp. at SH and BC ranged from 0.1 to 1.8%, respectively. Moreover, non-geniculate coralline algae dominated the subtidal substrate at SH, ranging between 60.2 and 69% at 15 and 10 m. The low cover of A. japonica in SS (at 5 m) coincided with a high percent cover of canopy-forming brown algae. However, canopy-forming brown algae were rare at all depths at SH and BC and were dominated instead by coralline algae and the scleractinian corals. This study, by utilizing a non-destructive method, provides a baseline qualitative and quantitative information for understanding the site and depth-dependent distribution of A. japonica and algal populations, which is important to understand climate change related changes in benthic communities in Jeju and elsewhere.

Assessing the state of marine biodiversity in the Northeast Atlantic

The Northeast Atlantic, a highly productive maritime area, has been exposed to a wide range of direct human pressures, such as fishing, shipping, coastal development, pollution, and non-indigenous species (NIS) introductions, in addition to anthropogenically-driven global climate change. Nonetheless, this regional sea supports a high diversity of species and habitats, whose functioning provides a variety of ecosystem services, essential for human welfare. In 2017, OSPAR, the Northeast Atlantic Regional Seas Commission, delivered an assessment of marine biodiversity for the Northeast Atlantic. This assessment examined biodiversity indicators separately to identify changes in Northeast Atlantic biodiversity, but stopped short of determining the status of biodiversity for many species and habitats. Here, we expand on this work and for the first time, a semi-quantitative approach is applied to evaluate holistically the state of Northeast Atlantic marine biodiversity across marine food webs, from plankton to top predators, via fish, pelagic and benthic habitats, including xeno-biodiversity (i.e. NIS). Our analysis reveals widespread degradation in marine ecosystems and biodiversity, particularly for marine birds and coastal bottlenose dolphins, as well as for benthic habitats and fish in some regions. The poor biodiversity status of these ecosystem components is likely the result of cumulative effects of human activities, such as habitat destruction or disturbance, overexploitation, eutrophication, the introduction of NIS, and climate change. Bright spots are also revealed, such as recent signs of recovery in some fish and marine bird communities and recovery in harbour and grey seal populations and the condition of coastal benthic communities in some regions. The status of many indicators across all ecosystem components, but particularly for the novel pelagic habitats, food webs and NIS indicators, however, remains uncertain due to gaps in data, unclear pressure-state relationships, and the non-linear influence of some pressures on biodiversity indicators. Improving monitoring and data access and increasing understanding of pressure-state relationships, including those that are non-linear, is therefore a priority for enabling future assessments, as is consistent and stable resourcing for expert involvement.

Organic Enrichment Induces Shifts in the Trophic Position of Infauna in a Subtropical Benthic Food Web, Hong Kong

Anthropogenic nutrient input to coastal waters is one of the most common disturbances within inshore marine benthic communities. Organic enrichment in sediments leads to the reduction or disappearance of sensitive organisms, and influences the quality and quantity of primary producers which serve as food sources for the benthic fauna. Such changes, in turn, affect the energy flow and food-web interactions in benthic communities. To examine how organic enrichment may alter marine benthic trophic relationship, a stable isotope (δ13C and δ15N) analysis of the potential food sources and a range of meiofauna and polychaetes from an organically polluted and a relatively unpolluted site was compared in subtropical waters of Hong Kong. Results indicated that some omnivorous infauna shifted from a mainly carnivorous diet at the unpolluted site to a largely herbivorous diet at the organically polluted site. This dietary shift is likely to be related to the oxygen stress, prey limitation and increased abundance and nutritional quality of primary producers in the eutrophic area, resulting in an increase in utilization of plant materials as the major food source. The present findings suggest that such changes in trophic position induced by organic enrichment can provide further insights into the structure and function of coastal benthic communities under pollution stress.

Humans at the top of the food web: are coastal benthic communities at Rapa Nui affected by fishing?

Humans at the top of the food web: are coastal benthic communities at Rapa Nui affected by fishing?

Biodiversity and Habitat Assessment of Coastal Benthic Communities in a Sub-Arctic Industrial Harbor Area

Coastal ecosystems face increasing anthropogenic pressures worldwide and their management requires a solid assessment and understanding of the cumulative impacts from human activities. This study evaluates the spatial variation of benthic macrofaunal communities, sediments, and heavy metals in the sub-Arctic coastal ecosystems around Sept-Îles (Québec, Canada)—a major port area in the Gulf of St. Lawrence. Physical sediment properties varied in the studied area, with a general sandy-silty profile except for specific locations in Baie des Sept Îles where higher organic matter and heavy metal concentrations were detected. Macrofaunal assemblages were evaluated for two taxa size classes (organisms &gt; 0.5 mm and &gt; 1 mm) and linked to habitat parameters using regression models. Communities of smaller organisms showed signs of perturbation for one assemblage close to industrial activities at Baie des Sept Îles, with an increased number of tolerant and opportunistic species, contrasting to neighboring regions whose compositions were similar to other ecosystems in the Gulf of St. Lawrence. This study enhances the understanding of sub-Arctic benthic communities and will contribute to monitoring programs for industrial harbor ecosystems.

Latitudinal consistency of biomass size spectra - benthic resilience despite environmental, taxonomic and functional trait variability

Global warming is expected to cause reductions in organism body size, a fundamental biological unit important in determining biological processes. Possible effects of increasing temperature on biomass size spectra in coastal benthic communities were investigated. We hypothesized higher proportions of smaller size classes in warmer conditions. Soft bottom infauna samples were collected in six Norwegian and Svalbard fjords, spanning wide latitudinal (60–81°N) and bottom water temperature gradients (from −2 to 8 °C). Investigated fjords differed in terms of environmental settings (e.g., pigments or organic carbon in sediments). The slopes of normalised biomass size spectra (NBSS) did not differ among the fjords, while the benthic biomass and NBSS intercepts varied and were related to chlorophyll a and δ13C in sediments. The size spectra based on both abundance and biomass remained consistent, regardless of the strong variability in macrofauna taxonomic and functional trait composition. Variable relationships between temperature and body size were noted for particular taxa. Our results indicate that while benthic biomass depends on the nutritional quality of organic matter, its partitioning among size classes is consistent and independent of environmental and biological variability. The observed size structure remains a persistent feature of studied communities and may be resilient to major climatic changes.

Development and application of a low-cost rapid assessment system for coastal benthic habitats.

Information on community structure and spatial distribution of benthic habitats are important in marine conservation and management. Coral areas, often monitored by trained scuba divers, are of importance for the ecosystem goods and services they provide. The data gathered may, however, be limited due to cost and time constraints. These restrictions and the continuing decline in coral reef health contribute to the need to develop rapid methods to efficiently document the distribution and status of coral reefs. A Rapid Assessment Instrument for Coastal Benthic Habitats (ARAICoBeH) System was developed to enable large-scale but low-cost coastal benthic habitat characterization and mapping without compromising accuracy. Inquiries on community structure and status in coral-dominated areas are also possible with the data collected using the method. The instrument, as well as the data processing and mapping algorithm are described in detail in this paper. A comparative study was conducted between ARAICoBeH and the frequently used underwater photo transect method. Variables compared were percent coral cover, functional group diversity, community structure as well as time and monetary requirements. There were no significant differences in estimates of percent coral cover and diversity of benthic functional groups for majority of sites while estimates of community structure were very similar. ARAICoBeH is cheaper and requires less time to gather the same amount of data as that of the photo transect method. The spatial distribution of coastal benthic habitats and community structure of coral-dominated areas in El Nido, Palawan, Philippines, are included to illustrate the application of the method.

Effects of seasonal fluctuation of amazon river discharge on the spatial and temporal changes of meiofauna and nematodes in the amazonian coast

In the Amazonian coast seasonal changes of environmental characteristics are the main structuring factors of coastal benthic communities. Spatial and temporal variations in meiofauna and nematofauna were studied during rainy and dry seasons in the coastal zone of the Biological Reserve of Piratuba Lake (Bazil Amazonian coast). At each site (seven sites) five samples were taken in vegetated (inside the mangrove – 100 m from the border) and non-vegetated (outside of the mangrove – 100 m from the border) areas. Each sample was sliced in 0–2 cm, 2–5 cm and 5–10 cm deep layers. Water surface temperature and salinity were determined. Meiofauna was composed of 15 taxa: Nematoda, Copepoda, Ostracoda, Amphipoda, Cladocera, Isopoda, Acari, Polychaeta, Gastropoda, Turbellaria, Rotifera, Loricifera, Nemertea, Kinorhyncha, and Insect larvae. Nematoda (39 genera in 14 families) was the dominant group, accounting for 70% of the total individuals. Daptonema, Neochromadora, Hypodondolaimus, and Dichromadora were dominant. Only salinity significantly changed between seasons and was significantly higher in the dry season. Meiofauna and nematofauna density and richness were lower than those in other mangroves worldwide. The significant changes in meiofauna and nematofauna between seasons and depths were related to higher salinity and food availability during the dry season and more food and oxygen available close to the surface (0–2 cm depth). Meiofauna did not show significant differences between vegetated and non-vegetated areas; however, higher density and richness were generally recorded in the vegetated areas, where food is more abundant, and the substrate is more stable. Non-selective deposit-feeding nematodes were dominant in all areas, seasons and depths. During the rainy season, the second most abundant feeding group was predators/omnivores as a response to an increase in organic detritus, whereas epigrowth feeders were the second most abundant group during dry season due to increased phytoplankton and phytobenthic production.