Biopolymeric Carbon Research Articles

Metabarcoding Reveals Meiofaunal Diversity in Rhodolith Beds From SE Brazil

ABSTRACTRhodolith beds (RBs) are known to increase the seabed complexity and act as a hotspot, supporting a unique biodiversity. This increased structural complexity due to the presence of rhodolith nodules is expected to influence benthic diversity at a local scale. To investigate this further, we tested the hypothesis that high‐density rhodolith beds hold higher meiofaunal diversity than low‐density beds. We used metabarcoding (V9 hypervariable region from 18S SSU rRNA) on sediment samples from a region with extensive rhodolith beds in the Eastern Brazil Marine Ecoregion, with distinct areas covered by high‐ and low‐density beds. The sediment underneath high‐density beds showed higher food availability (biopolymeric carbon) and organic matter quality (protein content and protein‐to‐carbohydrate ratio); however, meiofaunal composition and phylogenetic diversity was similar among all rhodolith beds sampled in the study area. Shannon's diversity was lower in high‐density beds, which may be attributed to the higher organic matter content and quality supporting strong competitors, such as crustaceans and annelids that may dominate and suppress the presence of other meiofaunal taxa. Our results showed that rhodolith beds host a number of meiofaunal zoobenthos that are rarely sampled with traditional morphology‐based methods, and we suggest that metabarcoding may become an important complementary method to study rhodolith beds globally. As assessing biodiversity is a prerequisite for any conservation measures, this study can provide insights when managing valuable marine habitats.

Meiofauna at a tropical sandy beach in the SW Atlantic: the influence of seasonality on diversity.

Sandy beaches are dynamic environments housing a large diversity of organisms and providing important environmental services. Meiofaunal metazoan are small organisms that play a key role in the sediment. Their diversity, distribution and composition are driven by sedimentary and oceanographic parameters. Understanding the diversity patterns of marine meiofauna is critical in a changing world. In this study, we investigate if there is seasonal difference in meiofaunal assemblage composition and diversity along 1 year and if the marine seascapes dynamics (water masses with particular biogeochemical features, characterized by temperature, salinity, absolute dynamic topography, chromophoric dissolved organic material, chlorophyll-a, and normalized fluorescent line height), rainfall, and sediment parameters (total organic matter, carbonate, carbohydrate, protein, lipids, protein-to-carbohydrate, carbohydrate-to-lipids, and biopolymeric carbon) affect significatively meiofaunal diversity at a tropical sandy beach. We tested two hypotheses here: (i) meiofaunal diversity is higher during warmer months and its composition changes significatively among seasons along a year at a tropical sandy beach, and (ii) meiofaunal diversity metrics are significantly explained by marine seascapes characteristics and sediment parameters. We used metabarcoding (V9 hypervariable region from 18S gene) from sediment samples to assess the meiofaunal assemblage composition and diversity (phylogenetic diversity and Shannon's diversity) over a period of 1 year. Meiofauna was dominated by Crustacea (46% of sequence reads), Annelida (28% of sequence reads) and Nematoda (12% of sequence reads) in periods of the year with high temperatures (>25 °C), high salinity (>31.5 ppt), and calm waters. Our data support our initial hypotheses revealing a higher meiofaunal diversity (phylogenetic and Shannon's Diversity) and different composition during warmer periods of the year. Meiofaunal diversity was driven by a set of multiple variables, including biological variables (biopolymeric carbon) and organic matter quality (protein content, lipid content, and carbohydrate-to-lipid ratio).

Vertical distributions of organic matter components in sea ice near Cambridge Bay, Dease Strait, Canadian Archipelago

Ice algae thriving within sea ice play a crucial role in transferring energy to higher trophic levels and influencing biogeochemical processes in polar oceans; however, the distribution of organic matter within the ice interior is not well understood. This study aimed to investigate the vertical distribution of organic matter, including chlorophyll a (Chl-a), particulate organic carbon and nitrogen (POC and PON), carbohydrates (CHO), proteins (PRT), lipids (LIP), and food material (FM), within the sea ice. Samples were collected from the bottom, middle, and top sections of the sea ice column near Cambridge Bay during the spring of 2018. Based on the δ13C signature, biochemical composition, and POC contribution of biopolymeric carbon (BPC), the organic substances within the sea ice were predominantly attributed to marine autotrophs. While the highest concentrations of each parameter were observed at the sea ice bottom, notable concentrations were also found in the upper sections. The average sea ice column-integrated Chl-a concentration was 5.05 ± 2.26 mg m−2, with the bottom ice section contributing 59% (S.D. = ± 10%) to the total integration. The column-integrated concentrations of FM, BPC, POC, and PON were 2.05 ± 0.39, 1.10 ± 0.20, 1.47 ± 0.25, and 0.09 ± 0.03 g m−2, respectively. Contributions of the bottom ice section to these column-integrated concentrations varied for each parameter, with values of 20 ± 6, 21 ± 7, 19 ± 5, and 28 ± 7%, respectively. While the bottom ice section exhibited a substantial Chl-a contribution in line with previous studies, significantly higher contributions of the other parameters were observed in the upper sea ice sections. This suggests that the particulate matter within the interior of the sea ice could potentially serve as an additional food source for higher trophic grazers or act as a seeding material for a phytoplankton bloom during the ice melting season. Our findings highlight the importance of comprehensive field measurements encompassing the entire sea ice section to better understand the distribution of organic carbon pools within the sea ice in the Arctic Ocean.

Benthic Foraminifera and Productivity Regimes in the Kveithola Trough (Barents Sea)—Ecological Implications in a Changing Arctic and Actuopaleontological Meaning

The rapid response of benthic foraminifera to organic carbon flux to the seafloor makes them promising bioindicators for evaluating the organic carbon stored in marine sediments. Fjords have been described as hotspots for carbon burial, potentially playing a key role within the carbon cycle as climate regulators over multiple timescales. Nevertheless, little is known about organic carbon-rich sediments in Arctic open shelves and their role in global carbon sequestration. To this aim, four sites have been sampled along a W-E transect across the Kveithola Trough located in the NW Barents Sea. Living (stained) benthic foraminiferal density, biodiversity and vertical distribution in the sediment were analysed together with the biogeochemical and sedimentological data. We identified two main depositional environments based on the relationship between benthic foraminiferal assemblages and carbon content in the sediments: (1) an oligotrophic land-derived organic matter region located in the outer part of the trough influenced by the warm and saline Atlantic Water; and (2) a stressed eutrophic environment, with high-content of metabolizable organic matter in the inner part of the trough, which comprises the main drift and the Northern flank of the trough. The freshness and good nutritional quality of the organic matter detected in the inner region could be the result of the better preservation of the organic matter itself, basically driven by the rapid burial of fine-grained organic-rich sediments enhanced by the cold and less saline Arctic Water coming from the Barents Sea. We conclude that foraminifera provide a tool to describe the Kveithola depositional environment as a carbon burial hotspot in a changing Arctic area subjected to a pulse of fresh food intended as biopolymeric carbon.

Sources and degradation of organic matter and its relation to trophic status in the core sediments of a tropical mangrove ecosystem along the Southwest coast of India

Present study has been designed to reveal the organic matter sources (algal vs. terrestrial), trophic status, the role of diagenesis and the applicability of biogeochemical indicators in a highly urbanized tropical mangrove forest. This has been achieved through a multiproxy approach by investigating the downcore distribution of bulk elemental properties (Total organic carbon (TOC%), total nitrogen (TN%)), biochemical composition, phytopigments and total hydrolysable amino acids (THAA). Both cores have a strong increase in algal biomass in the upper more fine grained part while core C2 has higher land plant fraction in its lower part compared to C1. The THAA profile decreased downcore ranging from 6.07 to 602.93 μmol g−1, contributing 7–53% THAA-N and 6–23% THAA-C to the sediments. Amino acids namely, serine (Ser) and tyrosine (Tyr) suggesting the contribution of fresh plankton organic matter likely by bacterial activity, while valine (Val), phenylalanine (Phe), isoleucine (Iso) and leucine (Lue) indicated more land plant derived organic matter. The surface dominance of proteins (PRT) and phaeophytin (Phaeo) pigment supporting the change from a more land plant derived organic matter to a more aquatic/marine driven productivity in the upper core sediments. Biochemical ratio (PRT/CHO >1), biopolymeric carbon (BPC), algal contribution to BPC (AL%-BPC) and degradation index (DI) indicated eutrophication related with the increase in algal organic matter. Based on mol%, amino acids viz., glycine (Gly) and alanine (Ala) were significantly enriched in downcore diagenetically reworked sediments indicating the growth of bacterial colonies and the selective preservation of bacterial biomass. Organic matter transformation from labile form into refractory character and vice versa through bacterial reworking, plays a major role in the development from oligotrophy to hypertrophy in the Cochin lagoon. The increasing urbanization have caused anthropogenic induced change in sediment composition, and recent eutrophication changed a more land plant dominated aquatic system to enhanced algal productivity.

Biochemical Composition of Seston Reflecting the Physiological Status and Community Composition of Phytoplankton in a Temperate Coastal Embayment of Korea

The biochemical composition of seston along a salinity gradient were examined in the low-turbidity, temperate, estuarine embayment, Gwangyang Bay in Korea. Seasonal variations in sestonic protein (PRT), carbohydrate (CHO), and lipid (LIP) concentrations were analyzed to assess the effects of physiological status and taxonomic composition of phytoplankton. The concentrations of biochemical compounds displayed a close relationship with chlorophyll a (Chla). PRT:CHO ratios were high (>1.0) in the estuarine channel in warmer months and in whole bay in February, indicating a N-replete condition for phytoplankton growth. High CHO:LIP ratios (>2.5) in the saline deep-bay area during the warmer months (>2.0) emphasized the importance of temperature and photoperiod over nutritional conditions. The low POC:Chla (<200), molar C:N (~7) ratios, and biopolymeric carbon concentrations coupled with high primary productivity indicated a low detrital contribution to the particulate organic matter pool. Diatom dominance throughout the year contributed to consistently high carbohydrate concentrations. Furthermore, generalized additive models highlighted that phytoplankton community (i.e., size) structure may serve as an important descriptor of sestonic biochemical composition. Collectively, our results suggest that physiological and taxonomic features of phytoplankton play prominent roles in determining the biochemical composition of seston, supporting the fact that the ecosystem processes in Gwangyang Bay are largely based on phytoplankton dynamics.

Assessment of the quality and quantity of organic matter in the Rufiji mangrove surface sediments using biochemical composition

This study was carried out to investigate spatial changes in the quality and quantity of sedimentary organic matter in the Rufiji mangrove system, Tanzania. Sediment samples were collected from three sampling sites. Total organic matter in mangrove sediments ranged from 7.28 ± 2.02% to 10.58 ± 1.34%. Protein concentrations varied from 1,145.33 ± 20.33 μg/g to 2,747.50 ± 25.14 μg/g in the mangrove sediments. Total carbohydrates, lipids and biopolymeric carbon in mangrove sediments ranged between 1,110.50 ± 16.31 μg/g and 1,914.17 ± 27.79 μg/g, 1,436.50 ± 24.13 μg/g and 6,373.50 ± 25.79 μg/g, and 4,496 μg C/g and 10,231.50 μg C/g, respectively. Tannins and lignins in mangrove sediments varied from 817.67 ± 12.97 μg/g to 1786.50 ± 30.74 μg/g, while stable carbon isotope (δ13C) in Rufiji mangrove sediments ranged between –26.64 ± 0.10 ‰ and –25.48 ± 0.13 ‰. Higher protein:carbohydrate (PRT:CHO) at station 3 indicated the presence of freshly deposited organic matter. The high lipid:carbohydrate (LPD:CHO) ratios observed in the Rufiji mangrove systems pointed towards the high quality of labile organic matter which supports benthic fauna. PCA revealed the association of variables and their distribution on trends across sites of the Rufiji mangrove system.
 Keywords: Organic matter, biochemical composition, Rufiji, mangroves, sediments

Trophic assessment in South American Atlantic coastal lagoons: Linking water, sediment and diatom indicators

Within two coastal shallow lagoons, trophic state was assessed by integrating water and sediment chemical indicators such as the TRIX and the benthic biopolymeric carbon (BPC) trophic indicator, altogether with biological environmental indicators (diatom species characterization). Spatial and temporal behavior of TRIX and BPC indices suggest that water column trophic indicators reflect rather short-term variations in water quality changes, while benthic trophic indicators rather reflect consistent long-term trends which make them useful as enduring indicators of eutrophication. Canonical Correspondence Analysis (CCA) showed that both sediment and transitional water trophic state indices increased eutrophic conditions with a decreasing salinity and increasing total nutrients. Diatom species associated with elevated eutrophic condition such as Staurosirella martyi, Staurosira breviestriata, Amphora copulata, Amphora veneta, Nitzschia sp., and Bacillaria paradoxa, showed a positive correlation with both trophic indices. We highlight the need for considering sediment eutrophication indicators towards in monitoring programmes within shallow coastal lagoons.

Sedimentary organic matter composition from tropical ports with distinct geographic and morpho-hydrodynamic characteristics: Evaluation through multiple biochemical markers

Increasing coastal urbanization and shipping activity-related environmental pollution advocate the importance of assessment of port ecosystems. Fatty acid biomarkers, elemental components, and biopolymers were used to evaluate the composition of sedimentary organic matter and benthic trophic status of Kolkata (freshwater, enclosed docks) and Kandla (seawater, macrotidal) ports of India. The sediment fatty acid composition indicated relatively fresh and energy-rich organic matter of phytoplankton and bacterial origin inside Kolkata port than the outside riverine station and Kandla port. Biopolymeric carbon (BPC), used as an indicator of trophic status, revealed eutrophic condition in Kolkata port with high accumulation of organic matter of autochthonous origin, attributed to poor water flushing and input of anthropogenic wastes. In contrast, Kandla port was meso-oligotrophic, rich in bacteria, and terrestrial plant-derived materials. Such an assessment of ports' trophic status helps to evaluate the health of the ecosystem and in management practices.

Structural and functional response of coastal macrofaunal community to terrigenous input from the Po River (northern Adriatic Sea)

To assess the influence of river-derived material on the benthic ecosystem in the Po River prodelta area, we investigated the structural and functional features of macrofaunal invertebrates in 14 sites. Biodiversity, species composition, response and effect traits of the community were determined and related to the main sediment physical-chemical and nutritional features (biopolymeric carbon, BPC; protein to carbohydrate ratio, Prt/Cho ratio; phaeopigment to chlorophyll-a ratio, Phaeo/Chl-a), as well as contaminants. We found significant spatial differences in community structure and its functional expression between northern and southern stations, and between nearshore and offshore ones. The shallower stations located nearby the main river mouth displayed higher densities, diversity and functional redundancy compared to southern stations. The main discriminating factors for the community were the higher percentage of sand and Prt/Cho nearby the river mouth, and fine grain-size and high Phaeo/Chl-a at the southernmost and deeper stations. Contaminant concentrations did not seem to severely affect the macrofaunal community. Changes in community structure were due to the dominance of few species, which occurrence varied according to grain-size and organic matter quality that in turn were linked to the different magnitude of depositional loads in the investigated area.Focusing on response traits, we observed a clear influence of high loads nearby the main river mouth, through the dominance of sessile and tube-builder trait-categories at stations with a higher sand content. In contrast, we detected a major expression of burrowers and interface crawlers, and swimmers at southern and principally offshore muddy stations. Effect traits revealed that in the northern part of the prodelta prevailed suspension, surface deposit feeders and conveyor invertebrates that are, respectively, fundamental players in the benthic-pelagic coupling and elemental cycling within benthos. In the southern part, subsurface deposit feeder and biodiffuser organisms dominated. The latter are able to rework huge amounts of sediments also in the deepest layers, amplifying the elemental cycling and decomposition. In highly dynamic systems, as delta areas, the presence of invertebrates able to exploit different resources through bioturbation activities may enhance the functions of riverine costal ecosystems.

Bacterial diversity and microbial functional responses to organic matter composition and persistent organic pollutants in deltaic lagoon sediments

Lagoons in river deltas are highly productive systems that receive high loads of organic matter and nutrients. Among the major environmental stress factors and human health-related issues, the anthropogenic contamination is of particular concern, since coastal lagoons are intensively exploited for aquaculture activities. Although microbial communities constitute the most abundant fraction of the benthic biomass, also providing valuable ecosystem services, the links between sediment quality and microbial processes were largely disregarded. In this study, we aimed to elucidate whether different levels of riverine influence could provide favourable or adverse environmental conditions to sustain microbial diversity and processes. Sediments collected from four lagoons of the Po River delta were analysed to assess biochemical composition (biopolymeric carbon, Bio-PC), target organic pollutants (polycyclic aromatic hydrocarbons, PAHs; nonylphenols; bisphenol A), and microbial community properties (bacterial community composition, prokaryotic biomass, prokaryotic carbon production rate, PCP, community respiration rate, CR, extracellular enzyme activities, EEAs). The major physical and chemical sediment properties allowed identifying two statistically distinct groups of sediments with relatively low (LI) and high (HI) riverine influence. HI sediments were characterised by higher Bio-PC and PAHs concentrations, along with relatively high PAHs potential toxicity estimated by the Toxic Equivalent concentration approach. Contrasting results were obtained by linking the occurrence of dominant bacterial taxa (i.e.,Desulfobulbaceae and Desulfobacteraceae families) to sediment contamination patterns. Notably, the increasing pollution levels were likely to positively affect the occurrence of the Desulfuromonadales Sva1033 family, whereas detrimental effects were found against the family Ectothiorhodospiraceae. In addition, the concurrent increase of PCP/CR ratio along with key EEAs, highlighted that the benthic microbial community could consistently contribute to accelerate the degradation of persistent organic pollutants, with potential implication on the sediment self-purification processes.

Biochemical composition of sedimentary organic matter in the coral reefs of Lakshadweep Archipelago, Indian Ocean

ABSTRACTSurface sediments were collected from the shore and lagoons of Kavaratti, Kadamat Agatti and Pitti islands of Lakshadweep Archipelago during May 2015 and analysed for biochemical composition and quality of organic matter. The biochemical composition of sedimentary organic matter from the entire study area was characterised by the dominance of carbohydrates (CHO) followed by proteins (PRT) and finally lipids (LPD). PRT:CHO ratios were less than 1 and indicated the presence of aged organic matter in the islands. The poor nutritional quality of sediments to support benthic fauna was evident from the values of LPD:CHO ratios. The refractory nature of sediments and less availability of food to benthic source was supported by BPC:TOC ratios. Based on estimated ratios and biopolymeric carbon values, the trophic status of the study area was categorised as oligotrophic.

Mediterranean Coastal Lagoons: The Importance of Monitoring in Sediments the Biochemical Composition of Organic Matter.

Transitional water ecosystems are targeted by the European Union (EU) Water Framework Directive (WFD, CE 2000/60) monitoring programs in coastal zones. Concerning sediments, activities performed for the WFD focus on a few variables concerning the biochemical composition of organic matter. Our research reports the effects of oxygen availability on the biochemical composition of organic matter in sediments to highlight levels of targeted variables in time and, according to the depth of sediment layer, both under oxygenated and anoxic conditions in a mesocosm study on sediment cores. Results provide evidence that tested factors of interest (i.e., disturbance type, oxygenic versus anoxic conditions; persistence time of disturbance, 0–14 days; penetration through sedimentary layers, 0–10 cm depth) are able to significantly affect the biochemical composition of organic matter in sediments. Large part of the variables considered in this study (total organic carbon (TOC), total phosphorous (TP), total sulphur (TS), Fe, carbohydrates (CHO), total proteins (PRT), biopolymeric carbon (BPC), chlorophyll-a (Chl-a) are significantly affected and correlated to the oxygenation levels and could be good early indicators of important changes of environmental conditions. Monitoring activities performed under WFD guidelines and management strategies of Mediterranean coastal lagoon ecosystems shall include the biochemical composition of organic matter in sediment to provide an exhaustive picture of such dynamic ecosystems.

Living foraminiferal assemblages in two submarine canyons (Polcevera and Bisagno) of the Ligurian basin (Mediterranean Sea)

Living (Rose-Bengal stained) benthic foraminifera were investigated in eleven stations sampled along transects following a depth gradient from Polcevera and Bisagno canyons and the adjacent open slope (Ligurian Sea), in a depth interval ranging from 200 to 2000 m. In order to understand which environmental factors influence the abundance and taxonomical composition of the foraminiferal assemblages in these two domains (canyon and open slope), qualitative and quantitative foraminiferal data were correlated to the sediment biochemical composition (in terms of phytopigments, proteins, lipids, carbohydrates and biopolymeric carbon), grain size and the main hydrological characteristics (salinity, temperature, dissolved oxygen). The Cluster Analysis and Canonical Correspondence Analysis allowed us to detect two sectors (coastal and offshore) characterized by contrasting trophic conditions. The coastal sector reflects spread meso-eutrophic conditions in both physiographic domains being possibly more impacted by the river inputs and sediment transport processes from land. In fact, the narrow continental shelf of the Ligurian Sea favors the deposition of sediment transported by riverine processes on the immediately adjacent coastal areas. As a result homogenization of sea-bottom conditions occurs, leading to an unclear differentiation between open slope and canyon foraminiferal assemblages. Conversely, the offshore sector is less affected by physical disturbance due to the sedimentary flows decreasing in relation to the larger distance from the coastline. Consequently, the lower organic matter content and lower food quality (expressed in terms of contribution of the primary material to the biopolymeric carbon pool) lead to a more oligotrophic condition, which favors the development of peculiar assemblages dominated by Glomospira charoides, Ammolagena clavata and epifaunal taxa. The first finding ever of a warm tropical species (Amphistegina lessonii) in the Ligurian Sea sediments at 500-m depth can be considered the first evidence of upward expansion of tropical species to the Northern portion of the Mediterranean Sea, which is experiencing an evident water warming linked to the ongoing global climate change.

Spatial and temporal distribution in the biochemical composition of sedimentary organic matter in a tropical estuary along the west coast of India

Distribution of sedimentary organic matter was undertaken in Cochin estuary, the second largest wetland ecosystem in India. Surface sediment samples were collected from twenty-seven stations during 2016 constituting the pre- and post-monsoon periods. The sediment samples were analysed for labile fractions of biochemical constituents such as carbohydrates (CHO), proteins (PRT) and lipids (LPD). Irrespective of the sampling periods, proteins (71%, 38%) constitute the major labile fraction, followed by carbohydrate (23%, 36%) and finally lipids (5%, 24). The application of biochemical index using PRT:CHO ratio revealed the presence of freshly deposited as well as the presence of aged organic matter in the estuary. The LPD:CHO ratio revealed low nutritional quality of sedimentary organic matter during the pre-monsoon and enhanced quality in post-monsoon. The trophic state classification based on biopolymeric carbon (BPC), PRT and CHO values unveils the fact that estuarine sediment nature varied between mesotrophic, eutrophic and meso-oligotrophic status. Low BPC:TOC ratios were observed pointing less availability of food to benthic source, and the organic matter present was mainly refractory in nature.

Spatial distribution of organic geochemical record in the core sediments along the prominent zones of Central Kerala, India

The study investigated the origin, quality, composition, and trophic state of sedimentary organic matter (SOM) in core samples collected from three zones (Munambam, Vypin, Chettuva) of Central Kerala, India. The SOM exhibited enhanced levels for carbohydrate (CHO) followed by protein (PRT) and lipid (LPD); and phytopigment in the sediment followed the trend: Pheophytin (Pheo) > Carotenoid (carotend) > Chlorophyll-a (Chl-a) > Chlorophyll-b (Chl-b) > Chlorophyll-c (Chl-c). The low PRT: CHO ratio indicated a large amount of nonliving or aged organic matter in the sedimentary environment. Whereas the low Chl-a: Pheo ratio interprets the abundance of dead plant materials in the sediments. Correlation matrix showed strong association between organic matter and clay fraction of sediment. Furthermore, the strong interrelationships between biochemical components and chloropigments in all the zones suggested that SOM is strictly connected to phytodetritus deposition. Vypin zone near Vallarpadam Container Terminal revealed the presence of high biopolymeric carbon content. Besides, the PRT: CHO > 1 reflected the eutrophic condition at the same site but the low PRT: CHO ratio in the remaining stations displays the oligotrophic nature.

Multiple human pressures in coastal habitats: variation of meiofaunal assemblages associated with sewage discharge in a post-industrial area

Marine ecosystems are globally threatened by human activities, but some areas, such as those affected by abandoned industrial plants, show an overlap of acute and chronic impacts, which determine a considerable deterioration of their health status. Here we report the results of a research conducted on coastal sewers that discharge their loads in the highly contaminated area of Bagnoli-Coroglio (Tyrrhenian Sea, Western Mediterranean). The sampling area is characterized by heavy industrial activities (a steel plant using coal, iron and limestone) started in 1905 and ceased in 1990, which left widespread heavy metals and hydrocarbon contamination. After taking into account the potential influence of sediment grain size ranges through their inclusion as covariates in the analysis, we tested the potential impact of sewage discharge on the total abundance and multivariate structure of meiofaunal assemblages, as well as on the abundance of single taxa. The organic matter was analysed in terms of total phytopigment and biopolymeric carbon concentrations. Nematoda, Copepoda (including their nauplii), and Tardigrada were the most abundant meiofaunal taxa at all sites, but nematodes did not show a consistent pattern relative to the sewage outfalls. However, the sewer located in the historically most contaminated area showed a minimal abundance of all taxa, including nematodes, while copepods were relatively less abundant at the two southernmost sewers. Comparing the north vs. south site of the sewers, higher meiofaunal abundances were observed in the southward part, likely as a result of the local circulation. The results of this study indicate the general adaptation of meiofauna to multiple stressors (sewage discharge, superimposed to chronic industrial contamination) and its likely modulation by other local processes. They also provide relevant baseline information for future restoration interventions that would take into account the spatial variation of target organisms as needed.

Assessment of the trophic state of a hypersaline-carbonatic environment: Vermelha Lagoon (Brazil).

Vermelha Lagoon is a hypersaline shallow transitional ecosystem in the state of Rio de Janeiro (Brazil). This lagoon is located in the protected area of Massambaba, between the cities of Araruama and Saquarema (Brazil), and displays two quite uncommon particularities: it exhibits carbonate sedimentation and displays the development of Holocene stromatolites. Due to both particularities, the salt industry and property speculation have been, increasingly, generating anthropic pressures on this ecosystem. This study aims to apply a multiproxy approach to evaluate the trophic state of Vermelha Lagoon based on physicochemical parameters and geochemical data for the quantification and qualification of organic matter (OM), namely total organic carbon (TOC), total sulfur (TS), total phosphorus (TP) and biopolymeric carbon (BPC), including carbohydrates (CHO), lipids (LIP) and proteins (PTN). The CHO/TOC ratio values suggest that OM supplied to the sediment is of autochthonous origin and results, essentially, from microbial activity. The cluster analyses allowed the identification of four regions in Vermelha Lagoon. The Region I included stations located in shallow areas of the eastern sector of Vermelha lagoon affected by the impact of the artificial channel of connection with Araruama Lagoon. The Region II, under the influence of salt pans, is characterized by the highest values of BPC, namely CHO promoted by microbiological activity. The Region III include stations spread through the lagoon with high values of dissolved oxygen and lower values of TP. Stromatolites and microbial mattes growth was observed in some stations of this sector. Region IV, where the highest values of TOC and TS were found, represents depocenters of organic matter, located in general in depressed areas. Results of this work evidences that the Vermelha Lagoon is an eutrophic but alkaline and well oxygenated environment (at both water column and surface sediment) where the autotrophic activity is greater than heterotrophic one. These particular conditions make this a special and rare ecosystem.

Effects of increase glacier discharge on phytoplankton bloom dynamics and pelagic geochemistry in a high Arctic fjord

Arctic fjords experience extremely pronounced seasonal variability and spatial heterogeneity associated with changes in ice cover, glacial retreat and the intrusion of continental shelf’s adjacent water masses. Global warming intensifies natural environmental variability on these important systems, yet the regional and global effects of these processes are still poorly understood. In the present study, we examine seasonal and spatial variability in Kongsfjorden, on the western coast of Spitsbergen, Svalbard. We report hydrological, biological, and biogeochemical data collected during spring, summer, and fall 2012. Our results show a strong phytoplankton bloom with the highest chlorophyll a (Chla) levels ever reported in this area, peaking 15.5µg/L during late May and completely dominated by large diatoms at the inner fjord, that may sustain both pelagic and benthic production under weakly stratified conditions at the glacier front. A progressively stronger stratification of the water column during summer and fall was shaped by the intrusion of warm Atlantic water (T>3°C and Sal>34.65) into the fjord at around 100m depth, and by turbid freshwater plumes (T<1°C and Sal<34.65) at the surface due to glacier meltwater input. Biopolymeric carbon fractions and isotopic signatures of the particulate organic material (POM) revealed very fresh and labile material produced during the spring bloom (13C enriched, with values up to −22.7‰ at the highest Chl a peak, and high in carbohydrates and proteins content – up to 167 and 148µg/L, respectively-), and a clear and strong continental signature of the POM present during late summer and fall (13C depleted, with values averaging −26.5‰, and high in lipid content – up to 92µg/L-) when freshwater melting is accentuated. Our data evidence the importance of combining both physical (i.e. water mass dominance) and geochemical (i.e. characteristics of material released by glacier runoff) data in order to understand the timing, intensity and characteristics of the phytoplankton bloom in Kongsfjorden, a continuously changing system due to sustained warming. In a scenario where glacial retreat is predicted to increase the impacts of meltwater discharge and associated delivery of organic and inorganic material to the surrounding waters, special attention is required in order to predict the consequences for Arctic fjords and adjacent shelf ecosystems.

Biodiversity, feeding habits and reproductive strategies of benthic macrofauna in a protected area of the northern Adriatic Sea: a three-year study

The macrozoobenthic community at a sublittoral station located in the Marine Protected Area of Miramare, Gulf of Trieste (Italy) was investigated monthly from June 2002 to July 2005. Community variables were studied and related to food sources (particulate, total and biopolymeric carbon contents, benthic microalgae and meiofauna). In addition, the macrofaunal response to a heatwave that occurred in summer 2003 in the area was also explored. Univariate and multivariate analyses highlighted that the macrozoobenthic community structure shifted towards the end of the study. Diversity remained fairly stable throughout the study, despite the high turnover values. From a dominance of short-lived invertebrates related to irregular fresh organic matter inputs, the community shifted toward long-lived taxa, principally related to an increase of biopolymeric C and microalgal biomass. Semelparous invertebrates seem to be less resistant to high temperatures compared to iteroparous ones. The latter proved to be capable competitors since they prevailed over the semelparous species towards the end of the study.The community exhibited a certain degree of resistance to high temperature, due to the adaptation of the macrofaunal invertebrates to this particular stress, induced by the wide natural fluctuations in temperature that occur on a seasonal basis in the Gulf of Trieste. This study highlights the importance of long datasets to assess the state and ecological processes of the macrofaunal communities.