Benthic Species Diversity Research Articles

Diversity of marine benthic species of Nostocales (Cyanobacteria) in Veracruz, Mexico

Background: Nostocales is a widely distributed, monophyletic order of cyanobacteria, whose species are mainly characterized by the presence of specialized structures such as heterocytes and akinetes. Despite being the most diverse group in marine environments, little is known about coastal species in Mexico. Particularly in Veracruz, only 17 species have been recorded, without photographic, morphological references, or ecological data; these records are only mentioned in floristic lists.
 Questions and / or Hypotheses: The present study aimed to contribute to the knowledge of the diversity of benthic marine Nostocales species in Veracruz, Mexico, as well as to provide detailed descriptions and illustrations of the species found, which can serve as a reference in subsequent studies.
 Study site and dates: Collect of cyanobacterial growths were made in three locations throughout Veracruz in 2020.
 Methods: The organisms were isolated from the field material. With the use of specialized taxonomic keys, they were morphologically identified, described and photographed.
 Results: A total of 20 Nostocales species were obtained, of which 17 were additions to the phycoflora of Veracruz, constituting an increase of 55 %. Taxonomic notes are added highlighting their differences with the literature. One of the species was identified as cf. and seven as sp., because their characteristics fully coincided with the generic morphology, but did not completely concur with the literature.
 Conclusions: These suggest that several records could correspond to new taxon not yet described that must be confirmed with different molecular markers.

Before and after closed season for beach seine fishing in Ghana: Impact on benthic macroinvertebrates species diversity indices

AbstractBeach seine fishery provides a means of livelihood to many households in Africa and it is widely practiced in the coastal communities of Ghana due to the relatively cheaper operational cost. However, the small mesh sizes of beach seine nets and fishing activities that involve dragging a net through the nearshore seabed tend to destroy fish breeding grounds and capture juvenile fish and non‐target benthic macroinvertebrates, which get discarded. This study investigated the impact that before and after closed season for beach seine fishing had on macroinvertebrates species diversity indices at two Ghanaian beaches with different fishing pressures. The study was carried out at OLA and Sisimbo Beaches located in the Central Region of Ghana, taking advantage of the statutory 1‐month national fishing closed season in July 2022. Six (6) replicate sediment samples were taken at each beach after landing by beach seine fishers every month for 6 months, from April to June, and August to October, representing before and after closed season, respectively. Benthic macroinvertebrates were retrieved from the samples using appropriate protocols and subjected to indirect (Shannon, Simpson, Rényi) and direct (species abundance models, species accumulation models, multivariate statistics) measures of species diversity analyses. The indirect species diversity indices increased monotonically the following 2 months after closed season but reduced in the third month after closed season at both beaches. Conversely, the direct measures of diversity indices revealed that closed season for beach seine fishing improved species numbers and richness at both study beaches. This is the first report on the impact of a closed season on macroinvertebrates in any African country.

Distinguishing Coastal Habitats of Caribbean Panama with Benthic Foraminifera

Abstract Benthic foraminifera were collected from reef coral, seagrass and mangrove sediments of Almirante Bay, Caribbean Panama, to associate species and assemblages with habitats and environmental conditions related to degraded water quality. The three habitats occur in different adjacent areas within an embayed, patch-reef setting. We analyzed the relative abundance, diversity and community structure of benthic foraminiferal species > 63 µm in 17 sediment samples from < 2 m mean water depth. Results from hierarchical cluster analysis, analysis of similarity, similarity percentages, non-metric multidimensional scaling and Fisher's alpha diversity were compared from seagrass, mangrove and coral habitats and also between two areas with contrasting water quality as previously defined by hydrography and general water quality. Among the three neighboring habitats, assemblages are fairly similar but differ in species proportions. Overall, Ammonia parkinsoniana, indicative of relatively low and variable salinities, is a dominant taxon. Foraminiferal assemblages from mangroves had the lowest mean diversity, a common trend under reduced salinity conditions, and diversity appears to be regionally controlled by freshwater input. Planorbulina acervalis was dominant in seagrass beds. Low-diversity, stress-tolerant foraminiferal assemblages are present in samples from all three habitats, reflecting the bay's highly variable patch-reef structure, freshwater input, and possible hypoxia. Diversity is generally lower near the mainland than in the eastern bay off the island of Isla Colón. Environmental associations of the benthic foraminifera of Almirante Bay are baseline ecologic data for comparisons to coastal habitats formed before human occupation and have the potential to be used in the sedimentary record to assess the impact of anthropogenic disturbance.

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.

Impact of agricultural practices on ecosystem health of lagoons: a case study of the Keta Lagoon Complex in Ghana, West Africa

The paper reports on the current ecological health of the Keta Lagoon Complex by analyzing a suite of physical, chemical, and biological environmental conditions prevailing within it. Results are discussed in relation to the main human activity (i.e., agriculture) prevailing in its catchment. The current water quality of the lagoon has declined compared to data collected 20years ago with elevated levels in parameters such as nitrate, phosphate, turbidity, and temperature. Secchi disk depth, salinity, and dissolved oxygen levels in the lagoon have decreased. More than 60% of the total area of the lagoon is predicted to be currently unsuitable to support aquatic life. The Carlson's TSI estimated for the various zones of the lagoon ranged between 72.40 and 80.61 depicting a highly eutrophic lagoon, with about 90% of the total area studied confirmed to be experiencing some degree of eutrophication. The plankton index of biotic integrity also yielded high values of between 3 and 6 in most areas of the lagoon, thereby affirming the poor health of the lagoon. The diversity of phytoplankton and benthic macroinvertebrate species in the lagoon has reduced significantly in the last two decades with about 11 genera of phytoplankton missing in the present study. Benthic macroinvertebrate assemblage richness, evenness, and diversity have decreased from 3.6, 2.0, and 5.8 in 2008 to 1.2, 0.8, and 1.7 respectively, in the present study. Overall, the health of the Keta Lagoon remains poorer and continues to decline with no signs of recovery.

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.

Relationship of Maastrichtian–Thanetian benthic foraminiferal species diversity, palaeooxygenation, and palaeoproductivity in shallow waters of the Western Desert, Egypt

Benthic foraminiferal analysis (315 samples, 16,271 specimens) of the shallow water (< 100 m) Maastrichtian–Thanetian rocks from the Dakhla Oasis (Western Desert, Egypt) was studied to infer the inter–relationships between species diversity, palaeooxygenation, palaeoproductivity, and palaeodepth and changes at the Cretaceous–Paleogene (K/Pg) boundary. Positive and significant correlations are noted between these proxies, suggesting a well-oxygenated oligotrophic environment. However, a brief interval (mid–lower Maastrichtian) of increased palaeoproductivity with reduced diversity and oxygenation (ventilation) is noted (a characteristic of mesotrophic–eutrophic settings) that coincides with very shallow waters during a highstand system tract (HST) and dominated by the dysoxic agglutinated species Ammobaculites khargaensis. The diversity index, Fisher’s α (< 5), and paleodepth proxy (foraminiferal wall structure types) also suggest a shallow neritic (largely littoral) depth for the entire study interval. At the bottom of the study section (Planktic Foraminiferal Zones CF8b-CF7), species diversity, palaeooxygenation, and palaeoproductivity are high. From the K/Pg boundary to the post-K/Pg period, these variables are low and fluctuate with moderate species dominance. Data suggests an overall 40% benthic foraminiferal species (38% of agglutinated and 40% of calcareous extinct species) extinction rate after the K/Pg hiatus. The period immediately following the K/Pg boundary is characterized by increased basinal ventilation and decreased palaeoproductivity, which are attributed to changes in sea level and concurrent regional subsidence. However, as stable as the community structure was at or just after the K/Pg boundary, the changes in species composition (assemblage) were dramatic and marked by a change from a pre–K/Pg agglutinated–dominated fauna (Haplophragmoides–Ammobaculites) to a post–K/Pg calcareous one (Cibicodoides–Cibicides–Anomalinoides).

Two new deep-water species of squat lobsters (Crustacea: Anomura: Galatheoidea) from the Central and Southwest Indian Ridge

The high diversity and endemism of benthic species on seamounts are extensively documented. Although the number of squat lobster species from seamount habitats has increased, species from the Central Indian Ridge (CIR) and Southwest Indian Ridge (SWIR) systems remain largely unknown. The hydrothermally active Indian Ridge system harbours potential sites for future Seafloor Massive Sulphides (SMS) mining. Since seabed mining may create a long-lasting impact on the deep-sea ecosystems, it could harm the unique deep-sea life associated with mineral deposits. This study identified two undescribed squat lobster specimens: one from the genus Munidopsis Whiteaves, 1874 from the CIR system in water depths ranging from 1981 to 2033 m, and one from the genus Typhlonida Macpherson & Baba in Machordom, Ahyong, Andreakis, Baba, Buckley, Garcia-Jimenez, McCallum, Rodriguez-Flores & Macpherson, 2022 from the SWIR system in depths ranging from 2070 to 2404 m. Both new species may be distinguished morphologically and genetically based on the partial mitochondrial (mtCOI) gene. To generate baseline environmental and biodiversity data, efforts for accurate sampling and correct identification of biological species are required.

Ecosystem approach of artificial reef through trophic web modelling

Along the French coast of the Atlantic and English Channel in a high tidal regime, only a limited number of Artificial Reefs (ARs) had been immerged in very few localities in the aim to increase the local production of fisheries of such hard artificial substratum. Moreover, ARs design have been planned to increase the diversity, abundance and biomass of benthic species associated to hard-bottom. Does the deployment of such artificial structure improve the production and ecological functioning on such equipped areas? Trophic models describing the interaction between species at different trophic levels and based on the quantification of energy flow and matter in ecosystems are able to respond to this question. They allow the application of numerical methods for the characterization of emergent properties of the ecosystem, also called Ecological Network Analysis (ENA). Usually, these indices have been proposed as ecosystem health indicators as they have been demonstrated to be sensitive to different impacts on marine ecosystems. Here, Ecopath ecosystem models composed of 23 compartments, from phytoplankton to mammals, are built to describe the situation “Before” and “After” the implantation of ARs in two areas: the Rade of Cherbourg in the central part of the English Channel along the French coast, and in the south of the Bay of Biscay along the Landes coast. In addition, ENA indices are calculated for the two periods, “before” and “after” the implantation of artificial reefs to compare network functioning and the overall structural trophic web properties. In both areas, increase of benthic and fish compartments insure an increase of the system maturity; nevertheless, the high surge of planktinovorous fishes on the Landes AR showed a protection role of such AR than changes of planktonic preys.

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 &lt; 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.

Marine fish and benthic biota before the 2019 oil spill: A baseline dataset for monitoring programs and impact assessments at Rio Grande Norte state, Northeastern Brazil.

In 2019 an oil spill spread over more than 4000 km of the Brazilian coastline. Monitoring programs that allow for the evaluation of potential impacts on communities and ecosystems and their recovery through time are needed and rely on baseline information previous to the oil spill. Here we compiled qualitative and quantitative data available from 8 studies on fish and benthic species from different habitats of Rio Grande do Norte (RN) from 2007 to 2018. We assessed the number of species from different locations and compiled information on conservation status and human use. We mapped the study areas and habitats and overlapped them with those affected by the oil spill. The RN state has a high diversity of fish (175 species) and benthic species (285 species), of which more than half of fish (52%) and 2% of benthic species are threatened and 72,8% of fish and 7,9% of benthic species are of commercial interest. Information of most habitats is still poorly known (i.e.majority ofthe available data are from unique and punctual sampling), which may weaken future evaluations of the real impact of the oil spill. Nonetheless, it is possible to design reliable monitoring based on our dataset, persistent contamination and future loss of diversity.

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.

Effects of Water Quality on Spatio-Temporal Diversity of Benthic Macro-Invertebrate Species along the Selected Shores of Lake Victoria, Homa-Bay County, Kenya

Human-induced landscape alterations impact the ecological integrity of water resources by adversely affecting fresh water ecosystems, water-quality, habitat structure, flow regime, and biotic interactions. For instance fresh-water Lake Victoria continues to be affected by massive discharge of waste-waters and other pollutants from the surrounding basin which interfere with the ecological balance leading to adverse impact on benthic macro-invertebrates especially along the lake shores. The objective of this study was to investigate the effect of water quality on the diversity of benthic macro-invertebrates along the shores of Lake Victoria in Homa-Bay County, Kenya. Samples were taken at various beaches including Oluch Kimira River Mouth, Homa Bay Sewage discharge point and Mbita East of course way shoreline and examined for water quality parameters and the species diversity of benthic macro-invertebrates at monthly intervals between September 2019 and Feb 2020. The study was conducted during dry and wet seasons to help determine any changes in waste water discharges, water quality and benthic macro-invertebrates’ characteristics. The results showed significant differences between various sites along the 3 different sites. During both wet and dry periods, Oluch Kimira and Homa Bay recorded low DO levels (4.0±0.46 to 6.2±0.19) MgL-1, while Mbita East of the course way throughout the period recorded DO level of (5.6±0.23 to 7.7±0.17) MgL-1. The mean concentration of Ammonia,NH4(µgL¯¹) during the dry season was (6.32 ±.3.55 to 8.79±3.02) and during the wet season 12.16± 0.92 to 22.50 ± 0.52. The county government should implement the findings of this study, which provides baseline data for evaluating the trends in water quality and related changes in benthic-macro invertebrates biodiversity in Lake Victoria shorelines in Homa Bay County. The findings will also help in making policy decisions in order to support environmental protection in Lake Victoria.

Changes in Diversity and Species Composition Across Multiple Assemblages in the eastern Chukchi Sea During Two Contrasting Years are Consistent with Borealization

The Arctic Marine Biodiversity Observing Network monitors biological assemblages on taxonomic scales ranging from microbes to seabirds on the northeast Chukchi Sea shelf to improve understanding of their responses to changing environmental conditions, including climate change. Here, we compare two years, 2015 and 2017, the latter characterized by a much larger spatial extent of warmer, more saline Pacific waters within the study region. These environmental differences were associated with changes in the taxonomic diversity and species composition of eight different assemblages. Impacts included decreases in the diversity and abundance of benthic species and increases in the diversity and abundance of zooplankton and demersal fish. These observations are consistent with the expected patterns of borealization, a term that describes changes from polar to more southern or boreal conditions and that have been observed on other Arctic inflow shelves where there is communication with the global ocean. A decoupling of the seabird assemblage from other assemblages in 2017 suggests that seabirds were unable to fully adjust to changing prey conditions in 2017. Pronounced differences in the taxonomic composition and a substantial decline in taxonomic diversity of bacteria and protists in 2017 remain unexplained but suggest that these microbes are highly susceptible to changing conditions. Continued warming of the Chukchi Sea will likely result in further borealization, with differential impacts on pelagic and benthic communities.

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.

Impaired benthic macrofauna function 4\xa0years after sediment capping with activated carbon in the Grenland fjords, Norway

The sediments in the Grenland fjords in southern Norway are heavily contaminated by large emissions of dioxins and mercury from historic industrial activities. As a possible in situ remediation option, thin-layer sediment surface capping with powdered activated carbon (AC) mixed with clay was applied at two large test sites (10,000 and 40,000 m2) at 30-m and 95-m depths, respectively, in 2009. This paper describes the long-term biological effects of the AC treatment on marine benthic communities up to 4 years after treatment. Our results show that the capping with AC strongly reduced the benthic species diversity, abundance, and biomass by up to 90%. Vital functions in the benthic ecosystem such as particle reworking and bioirrigation of the sediment were also reduced, analyzed by using novel bioturbation and bioirrigation indices (BPc, BIPc, and IPc). Much of the initial effects observed after 1 and 14 months were still present after 49 months, indicating that the effects are long-lasting. These long-lasting negative ecological effects should be carefully considered before decisions are made on sediment remediation with powdered AC, especially in large areas, since important ecosystem functions can be impaired.

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.

Macrozoobenthos Diversity as a Bioindicator of Heavy Metal Pollution in Segara Anakan Lagoon, Cilacap District, Indonesia

Various methods are available for monitoring pollution levels in surface water and sediments, including using organisms as bioindicators. Segara Anakan Lagoon is an estuarine ecosystem that could be affected by contaminants transported by rivers. Pollution sources include pesticides and fertilizers from upstream agricultural areas, domestic waste, and shipping traffic. Macrozoobenthos are among the organisms commonly used as bioindicators of environmental pollution. Macrozoobenthos live at the bottom of the water column, and as deposit feeders, they lend themselves to use as bioindicators. The structure of the macrozoobenthos community in Segara Anakan has changed, as evidenced by the diversity and abundance of benthic species. Furthermore, environmental pollution parameters, such as heavy metal concentrations in water and sediments, are relatively high in the lagoon. Concentrations of Hg, Pb, Cd, and Cr varied among collection sites, with average concentrations of 0.04, 4.4, 1.2, and 1.4 ppm, respectively. In general, the abundance of macrozoobenthos was low at collection stations with high heavy metal concentrations, demonstrating that heavy metal pollution has occurred in Segara Anakan. Correlation tests between macrozoobenthos and heavy metal concentrations in water and sediments yielded r-values of > 0.8225 and 0.7473, respectively.

Diet Composition and Nutritional Niche Breadth Variability in Juvenile White Sharks (Carcharodon carcharias)

Establishing diets and dietary generalism in marine top predators is critical for understanding their ecological roles and responses to environmental fluctuations. Nutrition plays a key mediatory role in species-environment interactions, yet descriptions of marine predators’ diets are usually limited to the combinations of prey species consumed. Here we combined stomach contents analysis (n = 40), literature prey nutritional data and a multidimensional nutritional niche framework to establish the diet and niche breadths of white sharks (Carcharodon carcharias; mean ± SD precaudal length = 187.9 ± 46.4 cm, range = 123.8-369.0 cm) caught incidentally off New South Wales (NSW), Australia. Our nutritional framework also facilitated the incorporation of existing literature diet information for South African white sharks to further evaluate nutritional niches across populations and sizes. Although teleosts including pelagic Eastern Australian Salmon (Arripis trutta) were the predominant prey for juvenile white sharks in NSW, the diversity of benthic and reef-associated species and batoids suggests regular benthic foraging. Despite a small sample size (n = 18 and 19 males and females, respectively), there was evidence of increased batoid consumption by males relative to females, and a potential size-based increase in shark and mammal prey consumption, corroborating established ontogenetic increases in trophic level documented elsewhere for white sharks. Estimated nutritional intakes and niche breadths did not differ among sexes. Niche breadths were also similar between juvenile white sharks from Australia and South Africa. An increase in nutritional niche breadth with shark size was detected, associated with lipid consumption, which we suggest may relate to shifting nutritional goals linked with expanding migratory ranges.

Microfaunal Signals and Paleoenvironmental Reconstruction Sediments in Well Z-1, Offshore Dahomey Basin, South-Western Nigeria

Fifty ditch cutting rock samples from well Z-1, OPL 310 offshore Dahomey basin, south western Nigeria were analyzed for their microfaunal and lithofacies content for the purpose of reconstructing the environment of deposition. Standard techniques of foraminifera slide processing and analysis was followed for the recovery of foraminifera while the gamma ray log complemented the rock samples for the lithofacies analysis. The lithological analysis revealed two lithofacies units in a generally fining upward sequence. The basal sandstone unit is characteristically milky white to brownish, coarse-pebbly grained, sub-angular to round and poorly to well sort with intercalation of shale. This unit is overlain by light to dark grey, moderately hard and non-fissile shale/mudstone sequence with intercalation of sand. Accessory mineral assemblage present in the formations includes mica flakes, glauconite pellets, carbonaceous detritus and ferruginous materials. The basal sandstone unit belong to the Oshosun Formation while the upper shaly unit is typical of Afowo Formation. Microfaunal study showed good recovery of abundant and well diversified planktic and benthic foraminiferal species. Forty-two (42) planktic, sixty-five (65) benthic calcareous and one benthonic arenaceous foraminiferal species were recovered. Micropaleontologically, Paleoenvironmental deductions were based primarily on the assemblage, abundance and diversity of benthic foraminiferal species and presence or absence of planktic foraminifera. Accessory mineral presence also aided the interpretations. Integration of lithological and micropaleontological synthesis enhanced the delineation of two environmental subzones over the analyzed interval, the outer neritic and the upper bathyal depositional settings corresponding to Afowo and Oshosun Formation respectively. A lowstand prograding wedge which is a good exploration target offshore was recognized between intervals 3400 ft to 3500 ft. In conclusion, the rock succession studied, penetrated Afowo and Oshosun Formations, and were deposited in an environment ranging from outer neritic to upper bathyal settings.