Coastal Fauna Research Articles

Coastal Chronicles: Journey into the World of Coastal Systems

Coastal systems are complex and dynamic settings where the atmosphere, sea, and land combine to create a variety of landscapes, including coral reefs, beaches, and estuaries. These areas contribute to global sustainability initiatives delineated in the United Nations Sustainable Development Goals (SDGs), sustain biodiversity, and play crucial ecological and economic roles. For sustainable management and protection of coastal environments, it is imperative to possess an understanding of the physical attributes, biological constituents, and mechanisms that dictate their dynamics. The natural processes of tides, waves, and currents impact the geomorphology of coastal systems, resulting in the formation of features including dunes, beaches, estuaries, and deltas. Coastal vegetation that stabilizes sediments and supports a variety of habitats, like seagrasses, mangroves, and salt marshes, further enriches these landscapes. Fish, crabs, mollusks, and birds are among the coastal fauna that flourish in these habitats and add to the diversity of coastal life. However, human activities that accelerate natural processes like erosion, accretion, and sea-level riseuch as industrialization, pollution, and climate change pose an increasing threat to coastal systems. Thus, it is essential to use sustainable management techniques that strike a balance between development objectives and conservation initiatives. Coastal ecosystems must be protected and enhanced through the implementation of policies like Integrated Coastal Zone Management (ICZM), habitat restoration, and Marine Protected Areas (MPAs). A combination of mitigation and adaptation strategies, such as building coastal fortifications and promoting nature-based solutions, are also necessary for climate change adaption. We can ensure the resilience and vitality of coastal systems for present and future generations, as well as their sustained ecological and economic significance in the global environment, by tackling these intricate concerns cooperatively and comprehensively.

First scenic assessment of the Coiba National Park’s beaches (Panama)

Coiba National Park (PNC) is one of the most important marine protected areas in the Americas, as an essential part of the Eastern Tropical Pacific Marine Corridor. As a marine protected area, its main objective is biodiversity conservation, although nature-based tourism and nautical activities are allowed. This research focused on the application of the Coastal Scenery Evaluation System (CSES) method along the entire PNC coastline. Based on two field visits, covering more than 200 km of coastline, 42 beaches were identified and evaluated, the vast majority in highly natural conditions. Similarly, five beaches were analyzed for biological data associated with the diversity of coastal fauna, as a preliminary inventory. The result of the CSES fuzzy logic calculation classified 64% of the beaches in the two highest scenery grades, with only 3 beaches in class IV, and none in class V. Regarding the biological data, macroinvertebrates were mostly represented by 13 mollusks, 1 echinoderm and 1 crustacean. In addition to scientific results, the research identified those beaches with the potential to be certified as coastal scenery of heritage value. In conclusion, this evaluation will help guide nature-based tourism actions within the PNC, and will serve as a baseline for future monitoring of the impact that tourism activity may have on beach fauna and natural attributes.

The Coral Triangle and Strait of Malacca are two distinct hotspots of mangrove biodiversity

Knowledge of the biogeography of marine taxa has lagged significantly behind terrestrial ecosystems. A hotspot of marine biodiversity associated with coral reefs is known in the Coral Triangle of the Indo-West Pacific, but until now there was little data with which to evaluate broad patterns of species richness in the coastal fauna of ecosystems other than coral reefs. This data is critically needed for fauna with low functional redundancy like that of mangroves, that are vulnerable to habitat loss and rising sea levels. Here we show that the diversity of mangrove fauna is characterized by two distinct hotspots in the Indo-West Pacific, associated with two habitat types: fringe mangroves in the Coral Triangle, and riverine mangroves in the Strait of Malacca, between the west coast of Peninsular Malaysia and Sumatra. This finding, based on a family of slugs of which the systematics has been completely revised, illustrates an unexpected biogeographic pattern that emerged only after this taxon was studied intensively. Most organisms that live in the mangrove forests of Southeast Asia remain poorly known both taxonomically and ecologically, and the hotspot of diversity of onchidiid slugs in the riverine mangroves of the Strait of Malacca indicates that further biodiversity studies are needed to support effective conservation of mangrove biodiversity.

Taxonomic revision of the Ophidion holbrookii Putnam, 1874 (Ophidiiformes: Ophidiidae) species complex, with description of a new species from Brazil.

This study integrates morphological and molecular data to redefine the taxonomic limits of Ophidion holbrookii, as well as its geographic ranges, with the description of a new species from the eastern and southeastern coast of Brazil, South America. Ophidion zavalai n. sp. is described based on variations related to ontogeny and sexual development of swim bladder and sonic apparatus, which are likely important traits for species recognition. The description of O. zavalai n. sp. and the redefinition of distribution limits of O. holbrookii corroborate the existence of different complex species in the western Atlantic, revealing important gaps of knowledge regarding morphological variation and species habits. Ophidion zavalai n. sp. is the first species of Ophidion described from the southwestern Atlantic Ocean and contributes to evidence of a distinct coastal fauna in Brazil and surrounding areas of Argentina province.

Comparative Phylogeography, Historical Demography, and Population Genetics of Three Common Coastal Fauna in Spartina Marshes of the Northwestern Gulf of Mexico

Coastal wetlands worldwide are experiencing high rates of loss and degradation that may lead to a reduction in diversity in faunal populations. Since salt marsh habitats are subject to a multitude of stressors, evaluations of the genetic diversity, connectivity, and potential resilience of faunal communities within salt marsh habitats are relevant. This study characterizes mitochondrial DNA (mtDNA) diversity for three common faunal residents of salt marshes along the northern Gulf of Mexico. Gulf Killifish (Fundulus grandis) samples were characterized for 1077 bp of the concatenated nucleotide sequence corresponding to the Control Region and Nitrogen Dehydrogenase, Subunits 2 and 5. Daggerblade grass shrimp (Palaemon pugio) samples were characterized using 466 bp of 16sRNA sequence, and phloem-feeding planthoppers (Prokelisia marginata) were characterized using 372 bp of Cytochrome c Oxidase Subunit I (COI) sequence. For F. grandis, our data revealed high levels of haplotypic diversity, evidence of isolation by distance (IBD), and regional population structuring associated with the distribution of two distinct phylogroups and distinct historical demography signatures. P. pugio and P. marginata displayed low levels of haplotypic diversity and evidence of population structure, but both appear to contain only snapshots of the total potential diversity for these species in the Gulf of Mexico. Greater resolution of the patterns of historical demography of Gulf Killifish may be obtained in future studies by including localities from Florida and Mexico. For both P. pugio and planthoppers, future studies would benefit from the characterization of genetic markers with a higher degree of polymorphism. We conclude that despite these three species inhabiting the same habitats along the same stretch of coast, each is subject to a different combination of evolutionary forces, and this study was able to reconstruct differences in how the genetic variation in each of these species emerged, and how it is maintained.

Beachrocks of the last low sea level, substrate of the Great Amazon Reef system along the outer Guiana shelf

The Great Amazon Reef System is a living biogenic mesophotic reef ecosystem that has been recently described along the shelf break of Brazil. An oceanographic cruise was carried out in 2019 along the outer edge of the French Guiana Shelf. A side-scan sonar survey was conducted to locate reef outcrops and allowed twelve in situ 80- to 120-m depth dives and sampling of the reef rocks and peripheral sands. The majority of the hard rocks are composed of biological concretions. However, several fragments revealed the inside presence of sandstone clasts. These clasts, more or less enveloped by biogenic coatings, probably represent destroyed clasts of underlying or neighboring beachrock banks. Their dominant cement is micritic (high-magnesian calcite); the intergranular or extragranular porous field was later filled with low-magnesian sparry calcite. The sand or gravel that accumulated near the barrier mainly consists of the blunt debris of coastal fauna and flora associated with different carbonate or ferruginous neoformed ooids. At 104-m depth, ooids extracted from dive 11 samples dated from the start of MIS2 (27,370 cal yr BP) and attest to the presence of a significant coastal accumulation. At this same site, cementing did not take place until about 3500 years later (23,990 cal yr BP). The cement of a nearby beachrock indicates a much more recent age (16,170 cal yr BP). Lastly, the age of 4100 yr BP measured on the barnacles attached to the top of the reef attests to the late Holocene reef's biological activity.

Microplastics in the foreshore coastal waters, sediment, and coastal fauna of a highly populated megacity - A study on the effect of anthropogenic discharge on clams.

In this study, the microplastics (MPs) abundance, characteristics and their variations across three popular beaches of highly populated and largest megacity of India were documented using clams as an indicator species. The abundance of MPs in clams was 77.39MPsitems/g in soft tissue parts and 198.82items/individual, while in coastal waters and sediments the abundance was 537.5±95items/L and 10,568.3±3053.3items/kg respectively. The observed higher microplastic diversity integrated (MDII) indicates numerous sources contributing to microplastics pollution and higher microplastic index (MPI) indicates greater bioavailability of MPs to clams. The bulk of the microplastics recovered from clams (55.78%), coastal sediments (52.27%) and coastal sea waters (54%) belong to the <100μm size range, and were identified as LDPE and polypropylene, polyamide and polystyrene. This investigation tried to validate the potential trophic transfer concerns associated with clam intake to both human health and marine ecology.

Trash in paradise: marine debris on the beaches of San Andrés Island, Seaflower Biosphere Reserve, Colombian Caribbean

San Andres Island is one of the main touristic places in Colombia, and its main attractions are its sandy beaches and the marine coastal ecosystems, such as coral reef and seagrass beds. However improper behavior of both residents and tourists on solid residue disposal may threaten not only the aesthetic of the island ́s beaches, but also poses risk to marine life. The objective of this research was to assess the amount of litter on the main beaches of the island. We surveyed three popular beaches for ten weeks. We collected 9894 units of litter, equivalent to a weight of 23 212.47 g. Beach cleanliness was estimated using the Clean Coast Index, and two of the three sites resulted “extremely dirty”, while the third was classified as “dirty”. The majority of the litter was plastic (59.5 % of total weight), followed by glass (20.4 %). Due to the persistence and negative effects of solid waste on coastal fauna, it is necessary to improve the management of litter disposal, and improve educational programs for both residents and tourists, to increase their awareness on the problem.

Biogeography of the coastal fishes of the Socotra Archipelago: Challenging current ecoregional concepts.

The Socotra Archipelago, located in the eastern Gulf of Aden, has a unique marine environment, which combines tropical and ‘pseudo-temperate’ elements. An updated species inventory recently considered its coastal fish diversity the highest among Arabian ecoregions, necessitating to re-assess the ichthyogeographic position of the island group. The main aim of this study is to describe the distributional biogeography of its coastal fish fauna in relation to contemporary ichthyogeographic and ecoregional concepts. Inferences are drawn with regard to the marine biogeographic arrangement and ecoregional partitioning of the Arabian region. The main datasets comprise eight and twenty selected families including 404 and 898 species, respectively, from Arabian ecoregions. The Socotra Archipelago has close affinities to a putative ecoregion in the eastern Gulf of Aden that extends to southern Oman. It is more closely related to the Arabian Sea coast of Oman than to ecoregions in the Red Sea and a putative ecoregion in the western Gulf of Aden. The Gulf of Aden does not represent a consistent ecoregion in ichthyogeographic terms, because its eastern and western parts are less closely related to one another than to other ecoregions. The Socotra Archipelago and the eastern Gulf of Aden should therefore not be assigned to a joined province with Red Sea ecoregions. The coastal fish faunas of the southern Red Sea have close affinities with those of the western Gulf of Aden. The Arabian/Persian Gulf is least related to the other Arabian ecoregions. The authors posit the Socotra Archipelago as a distinct ecoregion, either on its own or in combination with affiliated mainland areas. This best reflects the ichthyogeographic data and the exceptionally high levels of fish and overall marine diversity. Two alternative ecoregional delineations are proposed, serving as working hypotheses for onward research.

Is Glacial Meltwater a Secondary Source of Legacy Contaminants to Arctic Coastal Food Webs?

Climate change-driven increases in air and sea temperatures are rapidly thawing the Arctic cryosphere with potential for remobilization and accumulation of legacy persistent organic pollutants (POPs) in adjacent coastal food webs. Here, we present concentrations of selected POPs in zooplankton (spatially and seasonally), as well as zoobenthos and sculpin (spatially) from Isfjorden, Svalbard. Herbivorous zooplankton contaminant concentrations were highest in May [e.g., ∑polychlorinated biphenyls (8PCB); 4.43, 95% CI: 2.72–6.3 ng/g lipid weight], coinciding with the final stages of the spring phytoplankton bloom, and lowest in August (∑8PCB; 1.6, 95% CI: 1.29–1.92 ng/g lipid weight) when zooplankton lipid content was highest, and the fjord was heavily impacted by sediment-laden terrestrial inputs. Slightly increasing concentrations of α-hexachlorocyclohexane (α-HCH) in zooplankton from June (1.18, 95% CI: 1.06–1.29 ng/g lipid weight) to August (1.57, 95% CI: 1.44–1.71 ng/g lipid weight), alongside a higher percentage of α-HCH enantiomeric fractions closer to racemic ranges, indicate that glacial meltwater is a secondary source of α-HCH to fjord zooplankton in late summer. Except for α-HCH, terrestrial inputs were generally associated with reduced POP concentrations in zooplankton, suggesting that increased glacial melt is not likely to significantly increase exposure of legacy POPs in coastal fauna.

Ecotourism motivations and segmentation in a Fauna Production Reserve in Ecuador

PurposeIn recent years, tourists have been progressively increasing their interest in the natural environment and its enjoyment. The objective of this study was: (1) identify the underlying variables or motivational dimensions in ecotourism; and (2) analyze the demand segmentation in ecotourism.Design/methodology/approachThe empirical analysis was carried out in “Puntilla de Santa Elena” Fauna Production Reserve in Ecuador. The sample consisted of 369 surveys obtained in situ. For the data analysis, a factor analysis and a nonhierarchical K-media segmentation were performed.FindingsThe results show six motivational dimensions in ecotourism: “Self-development and Interpersonal relationships,” “Building personal relationships,” “Escape and ego-defensive function,” “Marine nature,” “Terrestrial nature” and “Rewards.” Also, according to their motivations, three segments of ecotourists emerged: “Reward and escape,” “Marine nature” and “Multiple motives.”Research limitations/implicationsThe limitation is the temporality with which the study was carried out. Another limitation was the number of the samples used. As future lines of research, it is proposed to investigate the offer related to ecotourism products and services adapted to the demand segments found.Practical implicationsAmong the practical implications, operators and companies linked to the tourism sector can plan more efficient strategies, adapted to the specific needs of each segment to improve the satisfaction of tourists and the intentions of returning to the destination, providing greater benefit to the tourists, to the sustainable development of the destination and the community.Social implicationsThe findings of this research can help public institutions and private companies to improve the tourism supply, create sustainable plans and potentially develop more efficient marketing planning. Protected areas will benefit from information about demand. The communities will be able to elaborate products according to the motivations and found segments. Administrators will be able to create sustainable management plans for ecotourism.Originality/valueAs ecotourism grows, it is vital to understand the ecotourists' motivations and segmentation to improve each segment service offering. This study presents original results of the motivations and segmentation of the demand for ecotourism based on a reserve area for the production of coastal marine fauna. To obtain valid results, a study was carried out in Ecuador, this being a country with a great variety of flora and fauna ideal for ecotourism.

Kelp detritus: Unutilized productivity or an unacknowledged trophic resource?

Kelp beds are one of the most productive marine systems and, while little of this production is directly consumed, there is growing evidence that kelp detritus is an essential food source for many detrital and suspension feeders, and forms an important component of offshore sedimentary carbon pools. However, the extent of the contribution of kelp detritus to the nutrition of coastal fauna is not well resolved. In this study, we compare the contribution of phytoplankton, kelp detritus, and waste from fish cages to the diet of a sentinel suspension feeder, the blue mussel (Mytilus edulis) using stable isotopes. We found a significant depletion in both 13C and 15N in kelp tissue with age (distance from stipe to the deteriorating distal end of the kelp frond) which may have biased dietary estimates in previous studies which have applied isotopic source values derived from fresh kelp. Our mixing models indicate that macroalgal detritus formed 59% of the diet of the mussels in Berehaven, Bantry Bay, Ireland. We support the isotopic mixing model results by modelling the relative production of phytoplankton, kelp, and salmon farm waste, and found the supply of C and N from kelp and phytoplankton far exceeded the requirements of the mussels with much less coming from the nearby fish cages. Monthly chlorophyll measurements indicated there was only sufficient phytoplankton density to support mussel growth during the spring and autumn, explaining our observation of patterns in the relative importance of utilization of kelp detritus. Where there is pressure to harvest kelp beds, this study highlights the supporting ecosystem service they provide as an important dietary source in coastal food webs and emphasises the need for appropriate management measures for this resource.

Linking fish and crustacean taxonomic composition with seasonal contrasts in the soft-bottom intertidal zone.

The primary objective of this study was to investigate the seasonal fish and crustacean variations concerning taxonomic composition, species richness, and diversity in sandy beach habitat. For this purpose, we investigated the Sonmiani Hor lagoon area during four distinct seasons, i.e., northeast (NE) monsoon, pre-monsoon, south-west (SW) monsoon, and post-monsoon for one year. During each haul, the net was pulled about 100m along the beach in 0.5m depth. The results showed a strong linear correlation between the diversity index and equitability in fishes (r = 0.978). The diversity index was strong negatively correlated with the abundance and biomass (r = -0.978, -0.972, respectively). The physical attributes like sea surface water temperature and salinity showed a strong negative effect on species assemblages (r = -0.981 and -0.943, respectively). The mean air and water temperature illustrated approximately 3°C difference during NE and pre-monsoon seasons. However, salinity, pH, and electrical conductivity did not show any significant seasonal variabilities. Under the ecological indices, the fish species displayed higher diversity (H' = 3.19) during SW monsoon, whereas the lowest diversity was observed during pre-monsoon (H' = 1.58). The equitability and species richness, however, remained more noticeable during SW monsoon (J' = 0.81). The total number of individuals of fish and crustaceans reached 4799 with 3813 fish individuals and 986 individuals of crustaceans. A total of 27 families of fish while five crustacean families comprising of 30 genera and 38 fish species while ten genera and 17 species of crustaceans were recorded. Liza subviridis displayed the highest abundance among the sampled fish species. In conclusion, fish species constituted a significant part of the coastal fauna in the study area. The seasonal variations displayed distinct variations in fish species composition and diversity.

Cenozoic climatic changes drive evolution and dispersal of coastal benthic foraminifera in the Southern Ocean

The Antarctic coastal fauna is characterized by high endemism related to the progressive cooling of Antarctic waters and their isolation by the Antarctic Circumpolar Current. The origin of the Antarctic coastal fauna could involve either colonization from adjoining deep-sea areas or migration through the Drake Passage from sub-Antarctic areas. Here, we tested these hypotheses by comparing the morphology and genetics of benthic foraminifera collected from Antarctica, sub-Antarctic coastal settings in South Georgia, the Falkland Islands and Patagonian fjords. We analyzed four genera (Cassidulina, Globocassidulina, Cassidulinoides, Ehrenbergina) of the family Cassidulinidae that are represented by at least nine species in our samples. Focusing on the genera Globocassidulina and Cassidulinoides, our results showed that the first split between sub-Antarctic and Antarctic lineages took place during the mid-Miocene climate reorganization, probably about 20 to 17 million years ago (Ma). It was followed by a divergence between Antarctic species ~ 10 Ma, probably related to the cooling of deep water and vertical structuring of the water-column, as well as broadening and deepening of the continental shelf. The gene flow across the Drake Passage, as well as between South America and South Georgia, seems to have occurred from the Late Miocene to the Early Pliocene. It appears that climate warming during 7–5 Ma and the migration of the Polar Front breached biogeographic barriers and facilitated inter-species hybridization. The latest radiation coincided with glacial intensification (~ 2 Ma), which accelerated geographic fragmentation of populations, demographic changes, and genetic diversification in Antarctic species. Our results show that the evolution of Antarctic and sub-Antarctic coastal benthic foraminifera was linked to the tectonic and climatic history of the area, but their evolutionary response was not uniform and reflected species-specific ecological adaptations that influenced the dispersal patterns and biogeography of each species in different ways.

Diel oxygen fluctuation drives the thermal response and metabolic performance of coastal marine ectotherms.

Coastal marine systems are characterized by high levels of primary production that result in diel oxygen fluctuations from undersaturation to supersaturation. Constant normoxia, or 100% oxygen saturation, is therefore rare. Since the thermal sensitivity of invertebrates is directly linked to oxygen availability, we hypothesized that (i) the metabolic response of coastal marine invertebrates would be more sensitive to thermal stress when exposed to oxygen supersaturation rather than 100% oxygen saturation and (ii) natural diel fluctuation in oxygen availability rather than constant 100% oxygen saturation is a main driver of the thermal response. We tested the effects of oxygen regime on the metabolic rate, and haemocyanin and lactate levels, of velvet crabs (Necora puber) and blue mussels (Mytilus edulis), under rising temperatures (up to 24°C) in the laboratory. Oxygen supersaturation and photosynthetically induced diel oxygen fluctuation amplified animal metabolic thermal response significantly in both species, demonstrating that the natural variability of oxygen in coastal environments can provide considerable physiological benefits under ocean warming. Our study highlights the significance of integrating ecologically relevant oxygen variability into experimental assessments of animal physiology and thermal response, and predictions of metabolic performance under climate warming. Given the escalating intensity and frequency of climate anomalies, oxygen variation caused by coastal vegetation will likely become increasingly important in mitigating the effects of higher temperatures on coastal fauna.

Metal Concentrations in the Coastal Fauna of the Caspian Sea

Metal Concentrations in the Coastal Fauna of the Caspian Sea

Acoustic characteristics of a potentially important macroalgae, Sargassum horneri, for coastal fisheries

A species of macroalgae, Sargassum horneri, which has gas-filled vesicles, plays important roles as nursery grounds, feeding grounds, and hiding grounds for coastal fauna. In addition, it recently emerged as a new coastal fishery resource in Japan. However, its acoustic reflection intensity is unknown, resulting in the impossibility of quantitatively estimating its biomass via an acoustic survey with a quantitative echosounder. We measured the target strength (dB re 1 m2) of S. horneri and clarified its characteristics. The measurements were taken using a 120 kHz quantitative echosounder in the fishing port of Iwate Prefecture in June and July 2014. Seven samples were collected by scuba diving in the coastal waters surrounding the port. Each individual sample was divided every 30 cm, and each divided layer was suspended at a depth of about 4–5 m, and its target strength was measured. Then, we divided S. horneri into vesicles and other parts. Each part was exsiccated at 80 °C for over 10 h. The dry weights of the vesicle and algal body were then measured. The weight of the vesicles of S. horneri tended to increase with an increase in algal body weight. The target strength increased with increasing algal body weight (Target strength = 11.1 log10Weight -71.1, R2 = 0.81) and vesicle weight. We considered that the contribution of the gas in the vesicles to the target strength was high, which is similar to the swim bladder of fish, as the acoustic reflection intensity of the vesicle was as strong as what has been reported for the gas in the swim bladder, and the intensity increased owing to the increase in vesicle weight accompanying the increase in algal body weight. Thus, S. horneri biomass could be estimated by acoustic survey using the target strength revealed in our study.

Nasal compartmentalization in Kogiidae (Cetacea, Physeteroidea): insights from a new late Miocene dwarf sperm whale from the Pisco Formation

AbstractFacial compartmentalization in the skull of extant pygmy whales (Kogiidae) is a unique feature among cetaceans that allows for the housing of a wide array of organs responsible for echolocation. Recent fossil findings indicate a remarkable disparity of the facial bone organization in Miocene kogiids, but the significance of such a rearrangement for the evolution of the clade has been barely explored. Here we describe Kogia danomurai sp. nov., a late Miocene (c. 5.8 Ma) taxon from the Pisco Formation (Peru), based on a partially preserved skull with a new facial bone pattern. Phylogenetic analysis recovers K. danomurai as the most basal representative of the extant genus Kogia, displaying a combination of derived (incipiently developed and excavated sagittal facial crest) and plesiomorphic features (high position of the temporal fossa, and antorbital notch not transformed into a narrow slit). Furthermore, when compared with the extant Kogia, the facial patterning found in K. danomurai indicates differential development among the facial organs, implying different capabilities of sound production relative to extant Kogia spp. Different facial bone patterns are particularly notable within the multi‐species kogiid assemblage of the Pisco Formation, which suggests causal connections between different patterns and feeding ecologies (e.g. nekton piscivory and benthic foraging). At c. 5.8 Ma, K. danomurai was part of a cetacean community composed of clades typical of the late Miocene, and of other early representatives of extant taxa, a mixture probably representing an initial shift of the coastal faunas toward the ecosystem dynamics of the present‐day south‐eastern Pacific.

Sponges in a Changing Climate: Survival of Agelas oroides in a Warming Mediterranean Sea

Sponges hold a key role in benthic environments, and specifically in the Mediterranean Sea. Past events of mass mortality in sponge communities have been linked to extended periods of high-temperature anomalies, yet it is unknown how a gradual change, such as the constant rise in global seawater temperatures, will affect biodiversity. Here we present a case study of Agelas oroides, a common massive sponge in the Mediterranean Sea, found at a wide depth range of 1–150 m. Last documented in the 1970s, A. oroides was considered lost from the Israeli coastal fauna. However, its recent rediscovery in mesophotic depths, where environmental conditions are stable, provided an opportunity to examine whether it can survive the present conditions in the shallow Israeli coast – where temperatures increased by 3°C during the past 60 years, while the nutrients concentration decreased following the damming of the Nile River. To test this hypothesis, A. oroides individuals were collected during winter from mesophotic sponge grounds (100–120 m) and transplanted to a shallow rocky habitat (10 m). Control individuals were transplanted back to the mesophotic habitat. Sponge survival, temperature, and nutrient concentrations were measured in both habitats. The shallow-transplanted sponges’ survival decreased only when the ambient temperature exceeded 28°C. In contrast, the control group at the mesophotic depth, where the temperature never rose above 20°C, survived the duration of the experiment. Our findings suggest that a prolonged period of high temperatures may constitute a major factor in A. oroides survival and disappearance from the Israeli shallow habitats.

Comparative feeding strategies of yellowfin tuna around St Helena and adjacent seamounts of the South Atlantic Ocean

Yellowfin tuna are the mainstay of the traditional tuna fisheries in St Helena waters, but there is limited knowledge of their ecology and feeding behaviour in the area. In this study yellowfin tuna stomach contents were used to assess spatio-temporal changes in feeding strategy and consider the role of tuna in the local ecosystem. Comparisons of the feeding spectra of yellowfin tuna between inshore regions of St Helena and oceanic seamounts demonstrated that in both areas the species was largely piscivorous. In inshore waters yellowfin consumed more neritic fauna, including significant numbers of crab megalopa, whereas around seamounts the diet included a greater diversity of epi- and mesopelagic fish and squids. The most important fish prey species in inshore waters was the St Helena butterflyfish Chaetodon sanctahelenae, and around seamounts was the pufferfish Lagocephalus lagocephalus. Results indicate that the diet spectrum of yellowfin tuna in St Helena waters is relatively similar to those of conspecifics living in waters with relatively low productivity, with strategies indicative of food-poor ecosystems. The availability of coastal fauna may make areas around islands and seamounts more attractive for feeding aggregations of yellowfin tuna, compared to the open ocean. The relatively unselective feeding of yellowfin tuna means that stomachs can provide valuable data on the species diversity, particularly in remote areas with limited opportunities for dedicated research expeditions.