Marine Benthic Species Research Articles

Marine species and assemblage change foreshadowed by their thermal bias over Early Jurassic warming

A mismatch of species’ thermal preferences to their environment may indicate how they will respond to future climate change. Averaging this mismatch across species may forewarn that some assemblages will undergo greater reorganization, extirpation, and possibly extinction, than others. Here, we examine how regional warming determines species occupancy and assemblage composition of marine bivalves, brachiopods, and gastropods over one-million-year time steps during the Early Jurassic. Thermal bias, the difference between modelled regional temperatures and species’ long-term thermal optima, predicts a gradient of species occupancy response to warming. Species that become extirpated or extinct tend to have cooler temperature preferences than immigrating species, while regionally persisting species fell midway. Larger regional changes in summer seawater temperatures (up to +10 °C) strengthen the relationship between species thermal bias and the response gradient, which is also stronger for brachiopods than for bivalves, while the relationship collapses during severe seawater deoxygenation. At +3 °C regional seawater warming, around 5 % of pre-existing benthic species in a regional assemblage are extirpated, and immigrating species comprise around one-fourth of the new assemblage. Our results validate thermal bias as an indicator of immigration, persistence, extirpation, and extinction of marine benthic species and assemblages under modern-like magnitudes of climate change.

Seasonal Predictability of Bottom Temperatures Along the North American West Coast

AbstractBottom Temperature anomalies (BTA) along the North American West Coast strongly influence benthic and demersal marine species. However, to date seasonal BTA forecast efforts have been limited and sources of BTA predictability largely undiagnosed. Here, an empirical model called a Linear Inverse Model (LIM), constructed from a high‐resolution ocean reanalysis, is developed to predict North American West Coast BTAs and diagnose sources of predictive skill. The LIM is considerably more skillful than damped persistence, particularly in winter, with anomaly correlation (AC) skill values of 0.6 at 6‐month lead. Analysis of the LIM's dynamics shows that elevated BTA forecast skill is linked to developing El Niño‐Southern Oscillation (ENSO) events, driving predicted BTA responses whose peaks occur at longer leads with increasing latitude. Weaker ENSO‐related signals in the northern coastal region still yield high BTA skill because noise there is also weaker. Likewise, the LIM's forecast signal‐to‐noise ratio is highest for bathymetry depths of ∼50–150 m, maximizing forecast skill there. Together, these predictive components lead to “forecasts of opportunity” when LIM anticipates especially high prediction skill. For the top 20% of events identified by the LIM as the forecasts of opportunity, 6‐month lead BTA hindcasts have AC skill averaging 0.7, while the remaining 80% hindcasts have mean skill of only 0.4, suggesting that the LIM can leverage ENSO‐related predictability of BTA to produce skillful forecasts.

Okeanomitos corallinicola gen. and sp. nov. (Nostocales, Cyanobacteria), a new toxic marine heterocyte-forming Cyanobacterium from a coral reef.

Cyanobacterial mats supplanting coral and spreading coral diseases in tropical reefs, intensified by environmental shifts caused by human-induced pressures, nutrient enrichment, and global climate change, pose grave risks to the survival of coral ecosystems. In this study, we characterized Okeanomitos corallinicola gen. and sp. nov., a newly discovered toxic marine heterocyte-forming cyanobacterium isolated from a coral reef ecosystem of the South China Sea. Phylogenetic analysis, based on the 16S rRNA gene and the secondary structure of the 16S-23S rRNA intergenic region, placed this species in a clade distinct from closely related genera, that is, Sphaerospermopsis stricto sensu, Raphidiopsis, and Amphiheterocytum. The O. corallinicola is a marine benthic species lacking gas vesicles, distinguishing it from other members of the Aphanizomenonaceae family. The genome of O. corallinicola is large and exhibits diverse functional capabilities, potentially contributing to the resilience and adaptability of coral reef ecosystems. Invitro assays revealed that O. corallinicola demonstrates notable cytotoxic activity against various cancer cell lines, suggesting its potential as a source of novel anticancer compounds. Furthermore, the identification of residual saxitoxin biosynthesis function in the genome of O. corallinicola, a marine cyanobacteria, supports the theory that saxitoxin genes in cyanobacteria and dinoflagellates may have been horizontally transferred between them or may have originated from a shared ancestor. Overall, the identification and characterization of O. corallinicola provides valuable contributions to cyanobacterial taxonomy, offering novel perspectives on complex interactions within coral reef ecosystems.

Estimation of pop-up satellite archival tag initial surface position: applications for eastern Bering Sea crab research

BackgroundClimate change is reshaping Bering Sea crab distributions and recent population declines have elevated the urgency in understanding spatial dynamics in relation to management boundaries. While pop-up satellite archival tags (PSATs) can provide fishery-independent movement information, a high level of spatial resolution is needed to evaluate small-scale (i.e., 10 s of km) movements of crabs. Because PSATs drift at the surface prior to acquisition of a satellite-estimated location (via Argos), the accuracy of pop-up location (i.e., animal terminal position) estimates depends on the ability to accurately estimate drift error. We deployed PSATs (n = 36) on fixed-position moorings in Bristol Bay and Marmot Bay, Alaska to validate a new method to estimate tag pop-up location and an associated error ellipse that uses in situ drift data from surfaced tags to estimate drift error. Estimated pop-up location was compared to the location of tag surfacing (i.e., the tag’s fixed position) and to an alternative estimate (i.e., an early satellite-estimated location). Additional tags were deployed on mature male red king crab (Paralithodes camtschaticus) in Bristol Bay during 2020 (n = 84) and 2021 (n = 90) to compare estimates of tag drift error and crab displacement derived using the method.ResultsFor red king crab tags with pop-up location estimates in 2020 (n = 79) and 2021 (n = 46), mean drift error was 9% and 44% of mean crab displacement, respectively. For fixed-position PSATs with pop-up location estimates (n = 27), mean distance between the estimated pop-up location and the tag’s fixed position was 2.0 km, representing a mean improvement in accuracy of 51% over alternative estimates. Corresponding error ellipse estimates either encompassed the tag’s fixed position (n = 11) or their boundaries were a mean distance of 1.3 km (n = 16) from the fixed position.ConclusionsOur method improves pop-up location estimates for PSAT-tagged animals and is particularly well suited for crabs and other slow-moving benthic marine species. The improved estimates enhance PSAT utility for addressing management and ecological questions that require a fine spatial resolution, such as movement near management boundaries or defining essential habitat for important life history events.

Spontaneous intersibling polymorphism in the development of dopaminergic neuroendocrine cells in sea urchin larvae: impacts on the expansion of marine benthic species.

The plasticity of the nervous system plays a crucial role in shaping adaptive neural circuits and corresponding animal behaviors. Understanding the mechanisms underlying neural plasticity during development and its implications for animal adaptation constitutes an intriguing area of research. Sea urchin larvae offer a fascinating subject for investigation due to their remarkable evolutionary and ecological diversity, as well as their diverse developmental forms and behavioral patterns. We conducted immunochemical and histochemical analyses of serotonin-containing (5-HT-neurons) and dopamine-containing (DA-positive) neurons to study their developmental dynamics in two sea urchin species: Mesocentrotus nudus and Paracentrotus lividus. Our approach involved detailed visualization of 5-HT- and DA-positive neurons at gastrula-pluteus stages, coupled with behavioral assays to assess larval upward and downward swimming in the water column, with a focus on correlating cell numbers with larval swimming ability. The study reveals a heterochronic polymorphism in the appearance of post-oral DA-positive neuroendocrine cells and confirms the stable differentiation pattern of apical 5-HT neurons in larvae of both species. Notably, larvae of the same age exhibit a two- to four-fold difference in DA neurons. An increased number of DA neurons and application of dopamine positively correlate with larval downward swimming, whereas 5-HT-neurons and serotonin application induce upward swimming. The ratio of 5-HT/DA neurons determines the stage-dependent vertical distribution of larvae within the water column. Consequently, larvae from the same generation with a higher number of DA-positive neurons tend to remain at the bottom compared to those with fewer DA-positive neurons. The proportion of 5-HT and DA neurons within larvae of the same age underlies the different potentials of individuals for upward and downward swimming. A proposed model illustrates how coordination in humoral regulation, based on heterochrony in DA-positive neuroendocrine cell differentiation, influences larval behavior, mitigates competition between siblings, and ensures optimal population expansion. The study explores the evolutionary and ecological implications of these neuroendocrine adaptations in marine species.

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.

Overview of Predation by Birds, Cephalopods, Fish and Marine Mammals on Marine Benthic Amphipods

With about 8000 marine benthic species, the amphipod crustaceans form one of the richest animal groups of the worldwide Ocean. They have colonized a wide range of soft- and hard-bottom natural and artificial habitats extending from the intertidal to hadal zones. Moreover, they show a broad size spectrum, with numerous giant species exceeding 20 cm in length and some species smaller than 2 mm. When biofouling artificial hard surfaces, some tube-building species can form very dense populations comprising up to 100,000 individuals per square meter. Amphipods are important prey for fish and mammals. Along with cephalopod juveniles, they are also included in the trophic diet of shorebirds that consume amphipods mostly during the low tide on tidal flats. They display diel migration, which reinforces the predation by demersal fish in the suprabenthic zone just above the sea bed, as well as by pelagic fish in the water column. Despite their importance in terms of biodiversity and trophic transfer, no general overview is available on the role of benthic amphipods in marine ecosystem food webs. Various methods, including laboratory and field experiments, as well as the analysis of stomach contents and DNA extraction, have been used to identify the prey/predator trophic links. Based on an extensive literature review, this study discusses the role of marine benthic amphipods as potential food for higher trophic levels in natural and artificial hard-bottom communities created via the construction of offshore wind farms.

Both high and low dispersal? Apparently contradictory genetic patterns in the Antarctic littorinid gastropod Laevilacunaria antarctica

How the near-shore marine benthic communities survived Quaternary glaciations in Antarctica is a major question for Southern Ocean biogeographers. Several hypotheses that consider life-history traits, such as bathymetric ranges and developmental modes, have been proposed. Near-shore species with high dispersive potential are expected to show star-like genealogies, with broadly distributed haplotypes surrounded by closely related variants at low frequencies, a consequence of rapid population post-glacial expansion mediated by larvae. By contrast, shallow-water taxa with low dispersal potential are expected to evidence marked genetic structure or even consist of separate cryptic species, due to their survival in small refugial populations subject to repeated bottlenecks. In this study we performed phylogeographic analyses on the high-latitude littorinid Laevilacunaria antarctica across its distribution from maritime Antarctica to South Georgia. This species is a highly abundant near-shore gastropod, commonly found on macroalgae, with low autonomous vagility and exhibits benthic protected development with no free-living dispersive stages. Such characteristics make this species a suitable model to test the above hypotheses. Contrary to low dispersal potential predictions, L. antarctica comprises a single unstructured unit across its distribution in maritime Antarctica, exhibiting a typical high-dispersal star-like, short-branched genealogy centered on a dominant broadly distributed haplotype. The South Georgia population, however, consists of a separate genetic unit, strongly differentiated from those of the maritime Antarctic. We estimate that these two genetic groups separated ~1.2 My, long before the Last Glacial Maximum and evolved independently in these areas. Our results thus provide partial support for the expected pattern for a near-shore marine benthic species with low innate dispersive potential. On a wider geographic scale (maritime Antarctica vs South Georgia), our results in L. antarctica provide support for the expected pattern for a near-shore marine benthic species with low innate dispersive potential. However, on a narrower scale (maritime Antarctica) life-history characters including the close association of the species with macroalgae, would allow dispersal and a species with low dispersal potential exhibits paradoxically an absence of genetic structure across hundreds of kilometers probably mediated by rafting.

A novel approach for improving the spatiotemporal distribution modeling of marine benthic species by coupling a new GIS procedure with machine learning

In this study we developed and validated a new integrative method for constructing and assessing Species Distribution Models (SDMs) for marine benthic species across spatial and temporal scales. This methodology synthesizes four dimensions-latitude, longitude, depth and time-into a unified predictive output, achieved by integrating a novel GIS tool, Bathymetric Projection (BP) with machine learning algorithms. BP can extract multi-dimensional data from remote sensing and satellite-derived datasets across the oceanic water column, including latitude, longitude, depth, and time. This data is then mapped onto the ocean floor using a reference bathymetric layer. The resulting seafloor layer is a predictive variable within the SDMs for benthic species. The model output quantifies the probability of species occurrence, or habitat suitability, as determined by environmental conditions specific to the ocean floor across the four dimensions. We validated this approach using two benthic species from the Colombian Pacific Ocean: the White shrimp (Litopenaeus occidentalis) and the Coliflor shrimp (Solenocera agassizii). The model's performance ranged from 87% to 98%, as indicated by 30-fold cross-validation on test datasets. Depth ranges and monthly seasonal patterns were accurately predicted when compared to independent literature data, confirming the model's capability to generate precise spatiotemporal distributions for benthic species. This research underscores the necessity of incorporating depth and time into SDMs, given their critical interactions with latitude and longitude in determining species distribution. The methodology offers a valuable tool for informing decision-making processes in fisheries and environmental management by enhancing the predictive accuracy of spatiotemporal distributions for benthic species, thereby facilitating more holistic interpretations of habitat suitability.

Using regional‐scale predictive habitat models to assess protection and identify potential locations for additional management or monitoring for a species of conservation interest

Abstract Marine protected areas (MPAs) and associated management measures are being implemented to conserve marine benthic species. To make effective decisions, marine managers need data on the distributions of species of interest and anthropogenic pressures, but also the potential connectivity between habitat patches. To explore how predictive modelling can be utilized in such a process, a model was developed to predict the distribution of northern sea fan, Swiftia pallida, habitat around parts of Scotland, Northern Ireland, and Ireland. The predicted distribution of suitable habitat was compared with spatial data on mobile bottom‐contacting fishing activity, and the location of MPAs designated for benthic features, and the management measures within MPAs that restrict mobile bottom‐contacting fishing activity, which is the main pressure‐causing activity that S. pallida are sensitive to. Over 20% of predicted suitable habitat is within MPAs, over 10% is within MPA management measures and over 48% is within areas that have experienced no bottom contacting‐fishing activity, which is significantly higher than the equivalent values for the study region as a whole. However, patches were identified that potentially experience above average levels of fishing activity and remain unmanaged, including within MPAs designated for associated features. The analysis also highlighted patches that could be candidates for monitoring recovery and the locations of unknown populations. For each patch of suitable habitat, the number of other patches within 22 km, a previously published estimate of dispersal distance for S. pallida, was used as a proxy for connectedness. Connectedness was estimated to be greatest for patches towards the centre and west of the study region. The results indicate how the outputs of predictive distribution models can be used in conjunction with other data to prioritize areas for surveys and identify locations where effective management may facilitate conservation or the recovery of benthic species.

Ecological benefits of artificial light at night (ALAN): Accelerating the development and metamorphosis of marine shellfish larvae

Urbanization has led to increasing use of artificial light at night (ALAN), which has rapidly become an important source of pollution in many cities. To identify the ALAN effects on the embryonic development of the Pacific abalone Haliotis discus hannai, we first exposed larvae to natural light with a light period of 12 L:12D (control, Group CTR). We then exposed larvae to three different light regimes. Larvae in Group NL were exposed to full spectrum artificial light from 18:00 to 00:00 to simulate the lighting condition at night, whereas Groups BL and YL were illuminated at the same time interval with 450 nm of short-wavelength blue light and 560 nm of long-wavelength orange light, respectively, to simulate billboard lighting at night. There were significantly higher hatching success and metamorphosis rates of larvae in Group BL than in Group YL or CTR (P < 0.05). The larvae in Group YL had the highest abnormality rate and took the longest time to complete metamorphosis. Transcriptomic studies revealed significantly higher expression levels of genes related to RNA transport, DNA replication, and protein processing in endoplasmic reticulum pathways in Group BL compared to the other groups. In the metabolomic analysis, we identified prostaglandin B1, tyramine, d-fructose 6-phosphate, L-adrenaline, leukotriene C4, and arachidonic acid as differential metabolic markers, as they play a vital part in helping larvae adapt to different ALAN conditions. Multi-omics correlation analysis of pairwise comparisons between all of the groups suggested that the biosynthesis of unsaturated fatty acids (FAs) and arachidonic acid metabolism pathways were significantly enriched (P < 0.05). Further quantitative analysis of the fatty acid (FA) contents revealed that 42 out of 50 FAs were down-regulated in Group BL and up-regulated in Group YL, which suggested that the synthesis, catabolism, and metabolism of FAs are crucial for the larval response to different spectral components of ALAN. For the first time, we report positive rather than negative effects of artificial blue light at night on the embryonic development of a benthic marine species. These results are significant for unbiased and full-scale assessment of the ecological effects of ALAN and for understanding the structural stability of the marine benthic community.

A Study of Infaunal Abundance, Diversity and Distribution in Chettuva Mangrove, Kerala, India

&lt;abstract&gt; &lt;p&gt;This study investigates an account on the diversity and abundance of benthic infauna of Chettuva mangrove in Kerala. Marine benthic infaunal species are an important factor in marine ecosystems and play a chief ecological function in the mangrove ecosystem. This research article gives an overview of infaunal diversity associated with eight sites of Chettuva mangrove. The present study revealed that infaunal species are significantly moderate within this mangrove ecosystem.&lt;/p&gt; &lt;/abstract&gt;

Morphology and phylogeny of Prorocentrum porosum sp. nov. (Dinophyceae): A new benthic toxic dinoflagellate from the Atlantic and Pacific Oceans

A new marine benthic toxic Prorocentrum species is described from the tropical/subtropical regions of the Atlantic (Colombian Caribbean Sea and Northeast Brazil) and Pacific (Southern Japan) oceans. Morphological cell structures were examined using light (LM) and scanning electron (SEM) microscopy. Prorocentrum porosum sp. nov. was characterized by 35.9–50.2 μm long and 25.4–45.7 μm deep cells, covered by broadly ovoid symmetric thecal plates. The surface of both thecal plates is smooth and covered by randomly scattered kidney-shaped pores (n = 102–149), rounder towards the center, absent in the central part, and surrounded by a conspicuous marginal ring of about 69–92 evenly spaced pores. Broad V-shaped periflagellar area exhibiting flagellar and accessory pores. The molecular phylogenetic position of P. porosum sp. nov. was inferred using partial LSU rRNA gene (rDNA) and rDNA ITS sequences. This new species branched with high support in a Prorocentrum clade including P. caipirignum, P. hoffmannianum and P. cf. lima (P. lima morphotype 5 sensuZhang et al., 2015). Pairwise comparison of ITS1 and ITS2 transcripts with these closest relatives revealed the presence of compensatory base changes (CBCs), with the exception of P. cf. lima (P. lima morphotype 5), which only showed in ITS2 a hemi-CBC (HCBC) and two base changes that possibly induce a structural modification. Toxin analyses performed in two Colombian and Brazilian strains in the present study detected the presence of low amounts of okadaic acid.

The blue diatom Haslea ostrearia from the Indian Ocean coast of South Africa, with comparative analysis of Haslea organellar genomes

Haslea ostrearia represents the model species of blue diatoms, a cluster of benthic marine species all belonging to the genus Haslea, noticeable for producing a blue pigment called marennine famous for its greening activity on the gills of bivalves but also for its potential in biotechnology. The exact distribution of H. ostrearia is unknown. It has been long considered a cosmopolitan diatom, but recent studies provided evidence for cryptic diversity and the existence of several other blue species, some of them inhabiting places where diatoms described as H. ostrearia had previously been observed. Recently, a marine diatom with blue tips was isolated into clonal culture from a plankton net sample from Kei Mouth on the Indian Ocean coast of South Africa. It was identified as H. ostrearia through a combination of LM/SEM microscopy and molecular analysis. This constitutes the first established record of this species from South Africa and the Indian Ocean and the second record for the southern hemisphere. Molecular barcoding clearly discriminated the South African strain from an Australian strain and cox1 based molecular phylogeny associated it instead with strains from the French Atlantic Coast, raising questions about the dispersal of this species. The complete mitochondrial and plastid genomes were compared to those of Haslea nusantara and Haslea silbo. Multigene phylogenies performed with all protein-coding genes of the plastome and the mitogenome associated H. ostrearia with H. silbo. In addition, complete sequences of circular plasmids were obtained and one of them showed an important conservation with a plasmid found in H. silbo.

Spatial and temporal stability in the genetic structure of a marine crab despite a biogeographic break

Elucidating the processes responsible for maintaining the population connectivity of marine benthic species mediated by larval dispersal remains a fundamental question in marine ecology and fishery management. Understanding these processes becomes particularly important in areas with a biogeographic break and unidirectional water movement along the sides of the break. Based on variability at 4209 single-nucleotide polymorphisms in 234 individuals, we determine the genetic structure, temporal genetic stability, and gene flow among populations of the commercially important mola rock crab Metacarcinus edwardsii in a system in southern Chile with a biogeographic break at latitude 42°S. Specimens were collected at eight sites within its geographic distribution, with collection at four of these sites was performed twice. Using population genetic approaches, we found no evidence of geographic or temporal population differentiation. Similarly, we found no evidence of an effect on gene flow of the biogeographic break caused by the the West Wind Drift Current. Moreover, migration analyses supported gene flow among all sites but at different rates for different pairs of sites. Overall, our findings indicate that M. edwardsii comprises a single large population with high levels of gene flow among sites separated by over 1700 km and demonstrate temporal stability in its genetic structure.

Identifying environmental drivers of shell shape and size variation in a widely distributed marine bivalve along the Atlantic Patagonian coast

Since the impacts of climate change on marine benthic organisms are already detectable in many aspects, it is crucial to address the potential responses of marine organisms and their interactions with the environment. In particular, the study of phenotype traits along latitudinal gradients is a powerful tool for exploring species responses in a changing environment. This work aims to: i) Quantify the variation in shell shape and size of the stripped clam Ameghinomya antiqua (King, 1832) along a 1600 km latitudinal gradient in the Atlantic Patagonian coast using geometric morphometric (GM) methods; ii) Identify environmental effects on shell shape and size change, using generalized additive mixed models GAMMs; iii) Estimate the effect size of different factors influencing shell shape and size variation. The combination of GM and GAMM allowed the quantification and identification of previously unknown relationship between morphological axes of variation and environmental variables. Results suggest that salinity is the most important factor determining shell shape, mainly affecting the outline while temperature has a substantial but weaker effect. More elongated shells and longer ligaments are observed under (less favorable) conditions of low salinity and temperature. GAMM showed that chlorophyll-a concentration, used as a proxy for food supply, has the most significant effect on shell size, and shell growth does not match the somatic soft-tissue growth. These results may help to predict the effects of climate change on the size and shape of marine benthic species and bivalves in particular. Furthermore, they provide new insights for using shell size and shape as proxies for the reconstruction of past environments and climates.

Foraminifera of the Faneromeni section (Crete, Greece) reflect the palaeoenvironmental development towards the Messinian salinity crisis

A severe phase of disturbance around 7.17 Ma initiated an ongoing development towards the Messinian salinity crisis (MSC) of the Mediterranean. We present foraminiferal data from the Faneromeni section on Crete to understand how the astronomical cyclicity and the restriction phase starting at 7.17 Ma were reflected in a succession that was deposited on the continental shelf and characterized by a precession-dominated alternation of organic-enriched grey marls and sapropels and light-coloured homogeneous marls. Benthic and planktic abundance data show that the foraminifera are closely associated with precessional cyclicity. Similar as in other Mediterranean sections, the 7.17 Ma shift in benthic assemblages is sedimentologically expressed by the occurrence of the first distinct sapropel (Faneromeni cycle F18). At this level, throughout the Mediterranean a group of open marine benthic species intolerant to oxygen stress abruptly decreased in abundance with several species disappearing at or shortly after 7.17 Ma. These species were replaced by species indicating increasing stress, implying decreasing oxygen content of the bottom waters after 7.17 Ma. The data further suggests that sapropelic sediments dominated by Bolivina dilatata/spathulata were deposited under hypoxic conditions, rather than under continuous organic flux. Our data reflects a second step in the restriction of the Mediterranean between 6.8 and 6.7 Ma, indicated by decreasing benthic diversity and increasing abundances of planktic and benthic taxa considered tolerant of hypersalinity. An increase in water salinity has been suggested before, and if true, appears to have affected the bottom waters and the surface waters around the same time.

Experimental evidence suggesting temperature-driven dormancy in the planktotrophic larvae of the sea cucumber Isostichopus fuscus

ABSTRACT While larval ecology is central to the population dynamics of marine benthic species with multiphasic life histories, the adaptations of larvae to environmental variability remain incompletely understood in many species. Using the holothuroid echinoderm (sea cucumber) Isostichopus fuscus, we examined how a planktotrophic species can use pre-competency plasticity to withstand suboptimal conditions of temperature over extended periods. Five cohorts of propagules (embryos/larvae) were exposed to temperature treatments (28–29, 24–25 and 20–22°C) in standardized culture settings. Under the coldest temperatures (typical of offshore upwelling areas), development mirrored that obtained under warmer temperatures until the early auricularia stage, where development was arrested for ~5 months in a manner consistent with quiescence. When temperature was increased again, larvae quickly resumed development and settled; no lasting negative impact was noted. The findings suggest that the larvae can use a form of dormancy to withstand suboptimal oceanic conditions for indefinite periods of time until successful delivery to appropriate inshore locations, the habitat were I. fuscus is exclusively found.

Vertical distribution of Cyanobacteria of the marine rocky supralittoral of the cape Kilse-Burun (Meganom peninsula, the Black Sea)

The vertical (altitudes at 0.1; 0.3; 0.6; 0.9 and 1.2 m above mean sea level - MSL) distribution of Cyanobacteria in the supralittoral zone of the Cape Kilse-Burun (Meganom Peninsula) was characterized. A total of 20 species of Cyanobacteria have been recorded; their number at various altitudes varied from 6 to 9 (minimal at 0.9 m above MSL). As for the systematic composition, species of the Oscillatoriophycidae subclass were found on the entire range of altitudes. The high contribution of representatives of the Synechococcophycidae subclass was noted at altitudes of 0.3 and 0.6 m MSL. The orders Chroococcales and Oscillatoriales were dominant at 0.3 m MSL; and the order Nostocales - at 0.1 m MSL. Among the families, Rivulariaceae family was observed at all altitudes, with a predominance at 0.1 m and 1.2 m MSL. The genera Gloeocapsa , Aphanocapsa and Leptolyngbya (with a low contribution) have been recorded at almost all altitudes. Only the genus Calothrix at altitudes of 0.1 and 1.2 m MSL represented 25.0% and 37.5%, respectively. According to the substrate confinement, the noted microphytes belonged to the attached ones; benthic mesosaprobiont marine species predominated in the entire surveyed range of altitudes. Brackish-marine (except 0.9 m above sea level) and freshwater-brackish (except 0.1 m above sea level) species were noted almost all over the range, while only one freshwater species was recorded at 0.1 m MSL. Species with cosmopolitan and boreal-tropical distribution predominated at all altitudes. The share of the latter was the highest at 0.1 m MSL, which is probably due to the relatively low temperature of the substrate under conditions of maximum surf irrigation. The features of the vertical distribution of Cyanobacteria emphasize the specificity of the environmental conditions of the supralittoral biotope.

Local fishers experience can contribute to a better knowledge of marine resources in the Western Mediterranean Sea

In this study we explore fishers’ perceptions in the Ebro Delta area, Western Mediterranean, throughout structured questionnaires. Specifically, we compare the coherence of information provided by fishers with those resulting by scientific studies in terms of the status of demersal marine resources in the Ebro Delta area; we describe temporal trends of demersal key species in the area with fishers’ perceptions; and we explore the use of Local Ecological Knowledge (LEK) as an alternative data sources to reduce the gap of knowledge on the spatial distribution and temporal trends of sensitive and vulnerable benthic marine species. Our results document important changes in the bottom trawling activity in the study area and in the abundance of commercial species with time according to fishers’ perceptions. Our results mostly match quantitative information from national statistics and stock assessment analyses. In addition, we document important changes in the presence of Vulnerable Marine Ecosystems (VMEs) in the study area due to the by-catch of habitat forming species with time. According to fishers’ perceptions, habitat forming species occur in the area, but were more frequently captured incidentally in the 1980 s and 1990 s. Overall, our study evidences that fisher’s perception represents an important source of complementary information to describe bottom trawling fisheries characteristics and the long-term changes of demersal target species in the Western Mediterranean Sea. Moreover, it highlights that LEK can provide fundamental and additional information on ecosystem changes and it can be a useful tool to increase the knowledge on spatial distribution and on temporal trends of vulnerable benthic species.