Benthic Species Richness Research Articles

EARLY JURASSIC BENTHIC FORAMINIFERAL ECOLOGY FROM THE CENTRAL HIGH ATLAS MOUNTAINS, MOROCCO

Abstract The Central High Atlas Mountains of Morocco have an extensive record of Lower Jurassic deposits from the Tethyan Ocean. In the Amellago region, Ziz Valley, and Dadès Valley several fossilized reef outcrops preserve benthic foraminifera spanning the Pliensbachian and Toarcian stages. This study analyzes benthic foraminiferal assemblage changes across the bi-phased extinctions at the Pliensbachian/Toarcian boundary and the Jenkyns Event (also referred to as the Toarcian Oceanic Anoxic Event). In Pliensbachian samples, assemblages with abundant Glomospira sp., Glomospirella sp., Siphovalvulina sp., Haurania deserta, Placopsilina sp., Mesoendothyra sp., and Everticyclammina praevirguliana are observed. Following both the Pliensbachian/Toarcian boundary event and the Jenkyns Event, benthic foraminiferal density, evenness, and species richness decreased, indicating these communities underwent ecologic stress; however, loss of diversity was most substantial between samples that pre-date and post-date the Jenkyns Event. Whereas the Pliensbachian/Toarcian boundary event coincides with the demise of the large benthic foraminifera Mesoendothyra sp. and Everticyclammina praevirguliana, the Jenkyns Event was detrimental for most clades of benthic foraminifera, including many small, resilient taxa. Based on the evidence provided, we suggest that the Pliensbachian/Toarcian boundary and the Jenkyns Event were distinct events, potentially caused by distinct environmental perturbations.

The effect of habitat on benthic diatoms in subarctic ponds – differences between rock and sediment

Subarctic ecosystems represent a vulnerable environment for their biota and studying their habitats provides a better understanding of ongoing and accelerated environmental change. Literature suggests that habitat and environmental variables such as water chemistry jointly influence benthic algal species richness and assemblage composition. However, the combined effects of habitat and water chemistry on benthic algal communities are poorly understood especially in subarctic freshwaters. This study compared benthic diatom assemblages on rocks and on sediment and examined if environmental variables affect diatoms similarly in these habitats. A total of 20 subarctic ponds were sampled for diatoms on sediment and rock in summer 2022 in northern Fennoscandia. Differences in species richness and Pielou evenness between habitats were analysed by a paired Wilcoxon signed-rank test. The most significant environmental variables influencing diatom species richness were determined by generalized linear models. Differences in diatom assemblage compositions were analysed using non-metric multidimensional scaling, analysis of similarities, and Jaccard similarity index. Finally, to study how environmental variables shape diatom compositions on rock and sediment, a redundancy analysis was performed. According to our results species richness and evenness were significantly higher on sediment than on rock, and water pH was the major determinant for diatom richness in both habitats. Diatom assemblage composition did not differ between rocks and sediment, and composition was shaped by the same environmental variables such as pond surface area and water pH in both habitats. Our results support the prevailing conception that sediment habitat contains higher diatom species richness than rocks, while assemblage composition does not differ between these habitats. This study highlights the role of water pH on benthic diatoms regardless of their habitat. Given that global warming is expected to affect water pH levels, such a change will probably have a notable influence also on subarctic diatom communities in the future decades.

Taxonomy and abundance of epibenthic Prorocentrum (Dinophyceae) species from the tropical and subtropical Southwest Atlantic Ocean including a review of their global diversity and distribution

In the tropical and subtropical South Atlantic Ocean, studies on the taxonomy and abundance of benthic harmful algae are scarce and the region has been largely under investigated. In this study, morphological descriptions, molecular (LSU rDNA and ITS region) and abundance data of benthic Prorocentrum species from the tropical and subtropical Southwest Atlantic and three oceanic islands are presented. Moreover, a review of global benthic Prorocentrum species richness and distribution is presented. Eleven benthic Prorocentrum species were found in Brazil. Morphological and molecular data on P. borbonicum, P. hoffmannianum, P. lima species complex and P. rhathymum were provided. Prorocentrum panamense, P. cf. caipirignum, P. cf. concavum, P. cf. norrisianum, P. emarginatum/fukuyoi/sculptile complex and two not identified species were observed using scanning electron and/or light microscopy, and morphological descriptions are presented. Prorocentrum lima species complex was found at all investigated sites, in abundances up to 2 × 104 cells g−1 FW at the Northeast Brazil, while maximum abundance of all the remaining species did not exceed 1 × 103 cells g−1 FW. The Fernando de Noronha archipelago can be considered a hotspot of benthic Prorocentrum species diversity, with ten species registered. Data compiled in the literature review shows a clear latitudinal gradient with higher species richness in tropical and subtropical regions relative to temperate areas. It is also evident that there is a bias caused by taxonomic impediment and an uneven sampling effort, with many regions still to be investigated using a combined morphological and molecular effort. Therefore, the current knowledge on the global distribution of benthic Prorocentrum species is likely underestimated.

Environmental factors in the spatial variability of demersal fish in a subtropical estuary and adjacent continental shelf

Quarterly collections of demersal fish were conducted between 2014 and 2018 on the adjacent continental shelf and in the Paranaguá Estuarine Complex (PEC). Univariate and multivariate statistical analyses were used to determine the abundance, richness, and composition of demersal fish assemblages and to list predictor variables responsible for the variability in these ecological descriptors by applying generalized linear models. The collected specimens of demersal fish (n = 25,179) were distributed across 19 orders, 31 families, and 72 species. Fish richness was explained by the following predictor variables: the percentage of fine sand in the sediment, the richness of the benthic megafauna, and sampling sites. The abundance was associated with the predictor variables of the percentage of very fine sand in the sediment, percentage of silt in the sediment, salinity, and sampling sites. Canonical correspondence analysis showed that the fish assemblage composition was strongly associated with the salinity gradient and positively correlated with benthic megafaunal species richness. As it is one of the last remnants of the Atlantic Forest, declared by UNESCO as a Natural Heritage of Humanity, the patterns observed in this study will support PEC's coastal management of current developmental demands, particularly related to port activities.

The continental shelf seascape: a network of species and habitats

The diversity of benthic communities on continental shelves is tightly linked to the diversity of habitats. Therefore, considering seascape habitat composition can help to gain insights into the spatial variability of benthic communities and move away from single-habitats approaches. This perspective needs different analytical methods, such as network analysis that enable the study of complex ecological interactions. This work explores the relationships between habitat and benthic species diversity in the Menorca Channel (the Balearic Islands, western Mediterranean). The seascape in the study area is a mosaic of alternating biogenic and sandy habitats that increases the total benthic species richness. Of the 442 benthic species included in the analyses, 286 species are shared by the six habitats identified, contributing to ecological connectivity across the seascape; 73 generalist species inhabit all six habitats simultaneously, however, 156 species are specialists and are linked to a single habitat, particularly to biogenic habitats, which increases specialization and the vulnerability of the species to habitat fragmentation. The network approach shows a tight link between epibenthic species diversity and the distribution of habitats over the continental shelf, providing essential information for optimal conservation strategies that move from a focus on protecting the most sensitive habitats to marine conservation schemes that encompass a diversity of habitats.

Changes in reef benthic communities in Sumba Timur, East Nusa Tenggara, Indonesia

Abstract. Utama RS, Hadi TA, Hermanto B, Giyanto, Budiyanto A. 2022. Changes in reef benthic communities in Sumba Timur, East Nusa Tenggara, Indonesia.Biodiversitas 23: 677-687. Anthropogenic impacts and coral bleaching due to rising sea surface temperature have been severe and often, as of late on the worldwide scale, influencing the composition of coral reef benthic communities from coral to algal-ruled reefs (phase shift). In any case, coral reef phase shift does not continuously happen, considering corals can recoup when stressors occur. This considers points to examine the alteration in coral reef benthic communities and the relationship among benthic categories. The study was carried out in 2018 and 2021 at 10 stations within East Sumba, and East Nusa Tenggara. Underwater photo transect (UPT) was used to examine benthic cover at a depth of 6 to 9 m in reef slope. The result demonstrated that the benthic communities were slightly altered, especially hard coral, sponge, and other biotas. A slight recovery of hard coral cover is shown in 2021, followed by the decline of sponge and fleshy seaweed cover, which is shown in most observation sites. Acropora spp., Seriatopora spp., and Stylophora spp. were the three genera that increased in cover. The study also found the relationship between the benthic gradient and species richness and the number of colonies, which is gradient changes in benthic composition were in line with the change in hard coral species richness and colony numbers. Although hard coral increase significantly changes over time, it's not altered the coral communities.

Crustaceans of the Northwest Pacific Ocean: Species richness and distribution patterns

Biodiversity patterns of marine crustaceans are still unknown in many locations or might have been overlooked due to our knowledge gaps, despite increasing sampling and data sharing efforts during the last decades. By analysing big data extracted from open portals such as Ocean Biodiversity Information System (OBIS) and Global Biodiversity Information System (GBIF), we aim to revisit the distribution and biodiversity patterns of the highly speciose and abundant Crustacea in the Northwest Pacific (NWP) from shallowest depths to the deep sea. This study focussed on selected benthic and pelagic crustacean (sub) classes and their species richness, sampling effort, and expected species richness (ES50) using equal/sized hexagonal cells, 5° latitudinal bands, 500 m depth intervals were analyzed. Crustacean species richness was highest in the tropical Philippines as well as around the Japanese islands. Pelagic crustacean species richness peaked at 30° latitude and declined beyond that. Benthic taxa; however, depicted high levels of species richness across most of the latitudinal gradient, reaching its highest point at 45° latitude. Due to the prevalence of certain crustacean orders in the deep sea, benthic species richness showed a distribution pattern with two distinct peaks across bathymetric gradients; with highest species richness recorded at shallow-water depths and also at abyssal depths. The most important environmental drivers of benthic and pelagic crustacean species richness were primary productivity (positive correlation) and salinity (negative correlation). Our study provides first insights into biodiversity patterns of the highly diverse Crustacea in the NWP and highlights strong differences between benthic and pelagic taxa. The results presented here could help us to better understand whether benthic or pelagic taxa might respond differently to climate changes in the NWP based on their distinct physiological and biological characteristics. This information is crucial in establishing species management strategies and ecosystem restorations in both shallow water and deep-sea environments.

Benchmarking eleven biodiversity indicators based on environmental DNA surveys: More diverse functional traits and evolutionary lineages inside marine reserves

Abstract To mitigate the ongoing threats to coastal ecosystems, and the biodiversity erosion they are causing, marine‐protected areas (MPAs) have emerged as powerful and widespread conservation tools. Strictly no‐take MPAs, also called marine reserves, undeniably promote fish biomass and density, but it remains unclear how biodiversity responds to protection. Identifying which facets of biodiversity respond to protection is critical for the management of MPAs and the development of relevant conservation strategies towards the achievement of biodiversity targets. We collected 99 environmental DNA (eDNA) samples inside and outside nine marine reserves in the Mediterranean Sea to assess the effect of protection on 11 biodiversity indicators based on fish traits, phylogeny and vulnerability to fishing. We controlled for the effect of environmental heterogeneity (habitat, bathymetry, productivity, temperature and accessibility) using a principal component analysis, and for spatial autocorrelation due to potential unmeasured factors. We found a positive and significant effect of protection on only 3 out of 11 indicators: functional and phylogenic diversity but also the ratio between demerso‐pelagic and benthic species richness. Rather, total fish richness responded significantly and negatively to protection. We did not detect any significant effect of protection on threatened and elasmobranch species richness, probably due to their large home range compared to the size of Mediterranean marine reserves. Synthesis and applications: Our findings highlight the importance of looking beyond the mere number of species to fully depict and understand the effect of marine reserves on biodiversity and evaluate the effectiveness of conservation measures. Rather, we propose a dashboard of three eDNA‐based indicators that can provide an early signal of ecosystem deterioration or recovery. eDNA metabarcoding offers a powerful tool to supply site‐specific and standardized taxonomic‐, phylogenetic‐ and trait‐based biodiversity assessments, in complement to other classical techniques, such as visual censuses or video surveys, able to estimate species abundance but also individual life‐stage and size.

Benthic biodiversity near brine discharge sites in the Port of Rotterdam

The Port of Rotterdam is a heavily man-modified estuarine system, Europe's major seaport and home to a large number of chemical and petrochemical plants, many of which are supplied with distilled water from two demineralized water plants in Botlek and Maasvlakte. In this study, we assessed the ecological conditions near the brine outfalls and at a reference site unimpacted by brine, focusing on the benthic macrofaunal composition. Overall, the analysis of the communities and species revealed a similar macrobenthic composition, although with lower abundance and diversity compared to the nearby North Sea environment. The outfall area of the Botlek demineralized water plant, which is a dead-end entirely marine waterway with no to little currents in contrast to the well flushed brackish environment of the outfall of the Maasvlakte demineralized water plant, was characterized by the lowest abundance of benthic macroinvertebrates, species richness and Shannon diversity index. Higher biodiversity values at the Maasvlakte demineralized water plant compared to the reference site were also associated with the presence of a large biogenic reef of the Pacific oyster Crassostrea gigas with specimens of over 8 years estimated age being observed, however with many dead individuals recorded at the time of surveys. The outfall area of the Botlek demineralized water plant also had the highest disturbance levels according to the results of AZTI's Marine Biotic Index (AMBI) in conjunction with Benthos Ecosystem Quality Index (BEQI). Its community was dominated by the opportunistic native species Capitella capitata and Varicorbula gibba, and species typical for organic matter enrichment such as Alitta succinea (native), Streblospio cf shrubsolii (native) and Theora lubrica (invasive), which correlates well with higher levels of anthropogenic pollution in this area. Generalized linear model (GLM) and distance-based multivariate linear model (DistLM) showed that the distance from the outfalls was an important factor in terms of brine impacts however explaining a small part of the variation observed. Similarity percentage analysis (SIMPER), multivariate analysis, and permutational multivariate analysis (PERMANOVA) showed low similarity between and within study sites, confirming that high levels of heterogeneity exist within the estuarine system in terms of natural conditions and anthropogenic stress.

The Impacts of the Freezing–Thawing Process on Benthic Macroinvertebrate Communities in Riffles and Pools: A Case Study of China’s Glacier-Fed Stream

Glacier-fed streams are one of the environments most sensitive to global climate change. However, the effects of the freezing–thawing process on benthic macroinvertebrate communities in different habitats of glacier-fed streams are unclear. In this paper, we investigated benthic macroinvertebrates in riffles and pools of a glacier-fed stream in Xinjiang, China, during the pre-freezing period (November, 2018), freezing period (January 2019), and thawing period (April, 2019). Our results showed that the freezing–thawing process resulted in a decline in benthic macroinvertebrate species richness and diversity, both of which were attributed to the effects of the freezing–thawing process on habitat stability, water quality, and cycling of the stream ecosystems. During the whole freezing–thawing process, the indicator taxa of riffles were Rhithrogena sp. and Baetis sp., while the only indicator taxon of pools was Chironomus sp. The species richness, Margalef diversity, and EPT richness (Ephemeroptera, Plecoptera, and Trichoptera) of benthic macroinvertebrates in riffles were higher than those in pools, due to the higher habitat heterogeneity in the riffles. However, the density in riffles was significantly lower than that in pools during the freezing period (p < 0.05). Additionally, pools were dominated by taxa with higher resilience and resistance traits, such as “bi- or multi-voltine”, “abundant occurrence in drift”, and “small size at maturity”. This result indicated that pools provide a temporary refuge for benthic macroinvertebrates in the extreme environment of glacier-fed streams. The freezing–thawing process plays an essential role in the formation of the structure and function of the stream ecosystem. Our results can help us to further understand the winter ecological process of headwater streams, and provide a reference for stream biodiversity conservation in cold regions.

Non-native Dreissena associated with increased native benthic community abundance with greater lake depth

Although the typical interaction between non-native invasive species and native species is considered to be negative, in some cases, non-native species may facilitate native species. Zebra and quagga mussels (Dreissena spp.) are aggressive invaders in freshwater systems, and they can alter energy flow by diverting nutrients from pelagic to benthic food-webs. In the last two decades, quagga mussels have largely replaced zebra mussels in shallow regions of the Laurentian Great Lakes and colonized deeper waters previously devoid of all dreissenids. Here, we aim to characterize potential positive effects of dreissenids in relation to depth on the benthic community in lakes Michigan and Huron. For this study, we used benthic survey data collected from Lake Michigan in 2015 and Lake Huron in 2017 and annual U.S. EPA Great Lakes National Program Office Long-term Biology Monitoring Program data for both lakes from 1998 to 2019. Benthic species richness and abundance (excluding dreissenids) in both lakes were almost three-fold higher in the nearshore (<70 m) compared to offshore (>70 m) communities. We found that, even though abundance of benthic invertebrates decreased with increased depth, total benthos density and biomass were higher in the presence than in the absence of quagga mussels in both lakes. Moreover, increased quagga mussel density and biomass with depth offset the lower benthos density and biomass at deeper depths, and samples with dreissenids had high densities of oligochaetes in both nearshore and offshore communities. These patterns are consistent with facilitative effects of quagga mussels on both shallow and deep-water benthic communities.

Landscape Mapping, Ichnological and Benthic Foraminifera Trends in a Deep-Water Gateway, Discovery Gap, NE Atlantic

Multidisciplinary studies have allowed us to describe the abiotic landscapes and, thus, reveal the ichnological and benthic foraminifera trends in a deep-water gateway. Mesoscale landscape mapping is presented based on the bathymetric position index, substrate types and near-bottom water temperature. Four sediment cores, retrieved from the entrance, centre and exit of the gap, were subject to computed tomography, ichnological and benthic foraminifera studies. A high diversity of abiotic landscapes in the relatively small area of Discovery Gap is detected and its landscape is characterized by 23 landscape types. The most heterogeneous abiotic factor is a topography that is associated with sediment patchiness and substrate variability. The ichnological and tomographical studies of the sediment cores demonstrate lateral and temporal differences in the macrobenthic tracemaker behaviour. The ichnofossils assemblage of the sediment core can be assigned to the Zoophycos ichnofacies with a higher presence of Zoophycos in the entrance site of the gap and during glacial intervals. Higher benthic foraminifera diversity and species richness during the Holocene are also registered in the southern part of the gap compared to the northern part. The spatial and temporal differences in macro-benthos behavior and benthic foraminifera distribution in the deep-water gateway are proposed to relate to the topographical variations of the Antarctic Bottom Water and its influence on the hydrodynamic regime, nutrient transport, etc.

Evaluation of deep-water environmental conditions during the latest Maastrichtian-early Danian: Insights from the western south atlantic ocean

The Cretaceous-Paleogene (K-Pg) boundary extinction event affected planktic foraminiferal assemblages worldwide in a dramatic way, but deep sea benthic foraminiferal assemblages were not significantly impacted. However, possible impacts of massive early Danian volcanic eruptions, such as those related to the Deccan Traps, on benthic foraminiferal assemblages are not yet explored. Here we present geochemical and benthic foraminiferal data across the K-Pg boundary and within the earliest Danian interval at Deep Sea Drilling Project (DSDP) Site 356, located on the São Paulo Plateau, western South Atlantic Ocean. Maastrichtian to Danian benthic foraminiferal assemblages are well-preserved and suggest deposition at middle to lower bathyal paleodepths, under an oligotrophic regime with well-oxygenated bottom water conditions. As expected, the K-Pg boundary event did not significantly affect benthic foraminiferal assemblages at Site 356. However, during the early Danian, benthic foraminiferal species richness, heterogeneity, diversity and equitability presented overall opposite trends in relation to the Hg/TOC and Hg/CaCO3 ratios, as well as Hg concentrations, which we consider proxies for intensity of volcanic activity. Our results suggest a possible response of Danian middle to lower bathyal benthic foraminiferal assemblages at Site 356 to changes in bottom water condition possibly associated with massive volcanism eruptions.

Evolutionary drivers of the hump-shaped latitudinal gradient of benthic polychaete species richness along the Southeastern Pacific coast.

Latitudinal diversity gradients (LDG) and their explanatory factors are among the most challenging topics in macroecology and biogeography. Despite of its apparent generality, a growing body of evidence shows that ‘anomalous’ LDG (i.e., inverse or hump-shaped trends) are common among marine organisms along the Southeastern Pacific (SEP) coast. Here, we evaluate the shape of the LDG of marine benthic polychaetes and its underlying causes using a dataset of 643 species inhabiting the continental shelf (<200 m depth), using latitudinal bands with a spatial resolution of 0.5°, along the SEP (3–56° S). The explanatory value of six oceanographic (Sea Surface Temperature (SST), SST range, salinity, salinity range, primary productivity and shelf area), and one macroecological proxy (median latitudinal range of species) were assessed using a random forest model. The taxonomic structure was used to estimate the degree of niche conservatism of predictor variables and to estimate latitudinal trends in phylogenetic diversity, based on three indices (phylogenetic richness (PDSES), mean pairwise distance (MPDSES), and variation of pairwise distances (VPD)). The LDG exhibits a hump-shaped trend, with a maximum peak of species richness at ca. 42° S, declining towards northern and southern areas of SEP. The latitudinal pattern was also evident in local samples controlled by sampling effort. The random forest model had a high accuracy (pseudo-r2 = 0.95) and showed that the LDG could be explained by four variables (median latitudinal range, SST, salinity, and SST range), yet the functional relationship between species richness and these predictors was variable. A significant degree of phylogenetic conservatism was detected for the median latitudinal range and SST. PDSES increased toward the southern region, whereas VPD showed the opposite trend, both statistically significant. MPDSES has the same trend as PDSES, but it is not significant. Our results reinforce the idea that the south Chile fjord area, particularly the Chiloé region, was likely the evolutionary source of new species of marine polychaetes along SEP, creating a hotspot of diversity. Therefore, in the same way as the canonical LDG shows a decline in diversity while moving away from the tropics; on this case the decline occurs while moving away from Chiloé Island. These results, coupled with a strong phylogenetic signal of the main predictor variables suggest that processes operating mainly at evolutionary timescales govern the LDG.

The effect of heavy metals and physicochemical variables on benthic macroinvertebrate community structure in a tropical urban coastal lagoon

Benthic macroinvertebrates are key bioindicators of pollution and an important component of food chains on wetlands. Here, we investigated the effect of heavy metals and physicochemical variables on the benthic macroinvertebrates community structure in a tropical urban coastal lagoon in Ghana which is known for its importance in the support of migratory waterbirds. Sediment samples were collected from seven different sites in the lagoon and analyzed for heavy metals. The physicochemical characteristics of the overlying water, sediment organic matter and silt/clay content were determined at these sites. The benthic macroinvertebrates abundance, species richness and diversity at each of the sites were further determined. The results indicated low levels of Zn, Cr, Pb, Cu and Cd in the lagoon with chironomids being the dominant benthic macroinvertebrates. Overall, the benthic macroinvertebrates community structure was not affected by the levels of heavy metals as toxic units were less than one. The benthic macroinvertebrates community structure was generally influenced by the dissolved oxygen, temperature levels of the overlying water, silt/clay and organic matter in the sediment. Increased benthic macroinvertebrates abundance was associated with lower water temperatures and elevated levels of silt/clay and organic matter in the sediment.

Preliminary results of sediments eDNA metabarcoding along arctic fjord

Ecosystems of arctic fjords are exposed to various natural and human-induced stressors that shape the taxonomic structure and functioning. Glacial activity and meltwater inflows together with advection of sea water masses from shelves form variety of environmental gradients that have been shown to influence marine biota. Some of these stressors like sedimentation of inorganic matter, instabilities of bottom sediments or food supply have been recognized as drivers of benthic species richness and diversity with use of traditional (morphology based) methods (Węsławski et al. 2011, Włodarska-Kowalczuk et al. 2005, Włodarska-Kowalczuk et al. 2012). In this study we aimed to use eDNA metabarcoding based methods to discriminate ecological diversity of benthic Eukaryota along environmental gradient (fjord mouth – glacier) at 6 stations in Hornsund fjord (Svalbard). At each station we collected 9 surface sediment samples. To cover a wide diversity of eukaryotic taxa we sequenced mitochondrial COI and nuclear 18S VIV2 genes to. Computational pipeline (SLIM, Dufresne et al. 2019) was used to de-multiplexed sequences, cluster them into ASVs and then taxonomically assigned. For the COI marker we distinguished 4486 unique ASVs, which in majority (95%) remained unassigned but constituted 51% of all sequences. Among sequences with assigned taxonomy 98% of them belonged to Opisthokonta clade, which consisted of 12 phyla in majority Annelida (80% of seqences) followed by Nemertea (13%) and Echinodermata (6%). In case of 18S marker we obtained 1309 unique ASVs, almost 70% of them were taxonomically assigned, constituting almost 97% of all sequences. Seven clades were assessed with dominance of Opistokonta (44%) followed by Stramenopiles (29%) and Rhizaria (18%) of all sequences. Among Opistokonta we noted 17 phyla, which were dominated by Annelida (54% of sequences) with significant share of Arthropoda (20%), Nematoda (10%) and Nemertea (8%). Analysis of alpha diversity expressed as number of unique ASV and Shannon-Wiener index showed different results for COI and 18S markers. For the first marker we did no notice any trend along fjord except much lower indices at the station nearest to the glacier, while for the second marker we observed a decline of both indices from fjord mouth towards glacier, however when data were limited only to benthic metazoans (e.g. excluding Calanoida or Chaetognatha) the trend was not that evident. Our results show that eDNA metabarcoding based methods may be successfully used for diversity assessments of arctic benthic fauna. Among the two markers we used 18S V1V2 allowed to assign higher number of taxa, however high proportion of sequences belonged to non-benthic and unicellular organism. Nevertheless, using 18S V1V2 data we observer similar biodiversity pattern along fjord (desceasing biodiversity with decreasing distance to glacier) that is known from traditional, morphological studies.

Effects of aquatic vegetation cover (Schoenoplectus decipiens) on microalgal biomass and assemblage structure in temporary wetlands of a semi-arid region (Eastern Cape Karoo, South Africa)

Temporary depression wetlands are often overlooked from a conservation and research perspective, despite recent evidence suggesting that their cumulative contribution to biodiversity at the landscape level is substantial. Here, we present observations aimed at understanding the significance of macrophyte cover in relation to the lower trophic levels, more particularly microalgae, within these highly dynamic wetlands. Thirteen such wetlands were sampled during October 2015, December 2015 and March 2016 in the Eastern Cape Karoo region of South Africa, to test the hypotheses that densely vegetated wetlands will have lower microalgal biomass and smaller algal size classes than sparsely vegetated wetlands. PERMANOVA results indicated that neither planktonic nor benthic microalgal biomass differed significantly between macrophyte cover categories (sparse, moderate and extensive cover), although there was a strong difference between the planktonic and benthic biotopes themselves. Planktonic and benthic microalgal assemblages were dominated by cryptophytes and chrysophytes (flagellates) throughout the study, with smaller nanoplankton being more abundant in wetlands with moderate or extensive macrophyte cover and larger microplankton dominating sparsely vegetated sites. Median benthic diatom species richness and diversity were higher under sparse macrophyte cover, but these differences were not significant, and no convincing evidence was found for an effect of macrophyte cover on microalgal biomass and assemblage composition in these temporary wetlands. Using distance-based Redundancy Analysis, dissolved inorganic nitrogen appeared to be the only environmental predictor for which a significant relationship with microalgal assemblage composition was reported. This study adds to the evidence from other assemblages (e.g. invertebrates) suggesting that the generalist nature of species occupying these systems allows them to adapt to the ever-changing conditions typical of ephemeral environments.

Littoral Benthic Communities Under Effect of Heat Wave and Upwelling Events in the Ne Baltic Sea

Paalme, T.; Torn, K.; Martin, G.; Kotta, I., and Suursaar, Ü., 2020. Littoral benthic communities under effect of heat wave and upwelling events in NE Baltic Sea. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 133–137. Coconut Creek (Florida), ISSN 0749-0208.The Baltic Sea forms a dynamic marine habitat with strong latitudinal and longitudinal gradients in many essential environmental variables. This environmental setting controls pelagic and benthic biodiversity by providing very narrow ecological niches for species displaying varying tolerances to environmental factors such as salinity, temperature and turbidity. In this study, changes in benthic communities in relation to extreme weather conditions, such as the occurrence of heat waves (HW) and coastal upwelling (CU) events, were analyzed and described in the north-eastern Baltic Sea. In the summer of 2018, the maximum water temperatures in the studied coastal sea sections varied between 20 and 25°C at 5 m depth whereby recorded values were up 7°C higher compared to that of the long-term mean. However, daily water temperature showed remarkable variation due to upwelling events occurring on multiple occasions with extreme temperature shifts of 14°C being recorded within a period of a few days. In the NE Baltic Sea, salinity gradient is up to 7 PSU in outer areas and it falls to zero in bays with riverine impact. Salinity has significant importance on benthic species abundance, richness and distribution. A rapid increase in salinity was observed during upwelling events. Extraordinarily, heat wave accompanied with upwelling event caused the increase of zoobenthic biodiversity and species-specific response of abundances. In contrast, the effect on macrovegetation species composition and proportion of opportunistic species was rather negative.

Molecular diversity and spatial distribution of benthic foraminifera of the seamounts and adjacent abyssal plains in the tropical Western Pacific Ocean

Abstract Deep-sea systems are among the least understood ecosystems on Earth. Forming large proportions of deep-sea benthic communities, benthic foraminifera play important roles; however, their molecular diversity and distribution patterns in the deep-sea seamounts and abyssal plains of the tropical Western Pacific Ocean are poorly known. In this study, using next-generation sequencing, we investigated the molecular diversities and community compositions of benthic foraminifera of the tropical Western Pacific Ocean seamounts and adjacent abyssal plains, with water depth ranging between 263 and 5900 m. A region of the small subunit (SSU) rRNA gene (about 300 bp) was amplified with the foraminiferal-specific primers (s14F3-s17), and the PR2 database was selected as the reference database for sequence assignment. Monothalamiids were assigned most of the 1399 operational taxonomic units (OTUs) obtained. The foraminifera genetic novelty, with an average similarity of 91.33% to reference sequences in the deep sea, was extremely high. Comparing the different habitats, the foraminiferal diversities of the seamounts investigated were both higher than those of their adjacent abyssal plains. Clustering of results showed the foraminifera community composition of the Y3 Seamount to be most like that of its adjacent abyssal plain. Our study indicates that the foraminiferal diversity distribution patterns and community structures between the two seamounts differ, yet they resemble those of their adjacent abyssal plain areas. We infer the possibilities that seamounts are diversity hotspots, possessing particularly high benthic species richness, and that foraminifera spread from them to the adjacent abyssal plains. The results also revealed variations in foraminifera at different water depths and temperatures in seamounts and adjacent abyssal plains. Additionally, an extremely high genetic novelty of foraminifera was observed in these habitats, which points to a hotspot for the discovery of new foraminifera species in deep-sea systems.

Benthic Cnidaria community in the oceanic archipelago of Trindade and Martin Vaz, Southwestern Atlantic Ocean

Based on literature review, recent surveys, and specimens’ identification, we examined benthic cnidarian species richness across the oceanic Trindade and Martin Vaz Archipelago (TMA), Southwestern Atlantic Ocean. A total of 37 species (three Hydrozoa and 34 Anthozoa) are reported, including seven new records. The zooxanthellate scleractinian corals Montastraea cavernosa, Mussismilia hispida, Mussismilia leptophylla and Siderastrea stellata were the most commonly found species, while some species, such as the azooxanthellate coral Polycyahtus sp., were only found at one site. Although Martin Vaz Island has a lower diversity (11 species) compared to Trindade Island (37 species), fewer studies have been conducted in the former. Likewise, research in the TMA has focused on shallow water communities (<40 m depth), and comprehensive surveys of benthic Cnidaria species of mesophotic and deeper water habitats are needed. All data presented herein are discussed in the light of species ecology and distributional patterns and we also report tissue necrosis in some Octocorallia colonies.