Marine Biology最新文献

Sea hares are cryptic, herbivorous sea slugs present on many coral reefs worldwide. Although they are known to consume high quantities of macroalgae, they are rarely considered or quantified in assessing algal suppression. Their role as algal suppressors is not well understood, therefore this study sought to quantify sea hare herbivory on the abundant red algal genus Laurencia. The sea hares Aplysia dactylomela, Dolabella auricularia and Dolabella sp. were collected and used in herbivory trials in aquaria at Heron Island on the Southern Great Barrier Reef to quantify their rate of consumption. A. dactylomela consumed 76.9 g partially dried weight of Laurencia per 24-h, which was significantly more than the other species, with D. auricularia consuming an average of 22.5 g and Dolabella sp. consuming 37.4 g partially dried weight. Consumption of Laurencia by A. dactylomela increased with body size, with the exception of the smallest animals, which ate up to 12.5 times their body weight. D. auricularia consumed significantly more algae than was lost in control tanks. Although we observed Dolabella sp. feeding on Laurencia, the amount consumed was not significantly different to loss of algae in control tanks. The rate of herbivory on Laurencia by A. dactylomela is comparable or greater than that of more commonly studied reef herbivores such as fishes and urchins, which suggests that they may contribute to algal suppression on coral reefs and further studies are warranted to evaluate their possible role in coral-algal phase shift dynamics.

A 21-day continuous monitoring of a highly tridimensional forest of the black coral Antipathella subpinnata (Ellis and Solander 1786) was carried out in the NW Mediterranean Sea at 63 m depth using an autonomous lander to investigate the diel short-term dynamics of the vagile fauna associated to the forest. The survey allowed to assess several aspects of the forest attractiveness and its use, especially by the ichthyofauna, including (i) the diversity and shifts of the fish community inhabiting three layers of the environment (seafloor, canopy, water column) between four light phases (dawn, day, dusk, night), (ii) the diel rhythm in forest use of the red swallowtail perch Anthias anthias (Linnaeus 1758) and its sleeping behaviour in terms of fidelity towards resting sites, duration of rests, and awakenings triggers, and, finally, (iii) the influence of biotic and abiotic variables on the fish behaviour. Considering that, so far, only spot censuses have been carried out in these habitats, this study provides a dynamic approach to the study of biodiversity in temperate mesophotic coral forests and offers an insight into the functioning of these complex and vulnerable ecosystems.

Effective seabird conservation requires understanding their marine spatial ecology. Tracking can reveal details of their foraging ecology and habitat use, as well as the suitability of marine protected areas for at-sea conservation, but results are often regionally specific. Here we characterised the foraging behaviour of tropical breeding brown boobies Sula leucogaster in the Chagos Archipelago, Western Indian Ocean, and tested habitat requirements. GPS tracking of thirteen individuals from two colonies, located 142 km apart on the same atoll (Great Chagos Bank), showed similar foraging effort and habitat preferences despite differences in season and breeding stage. Brown boobies from both tracked populations foraged close to the colony along the atoll shelf edge, avoiding deep oceanic areas and shallow waters of the Great Chagos Bank atoll, but within the Chagos Archipelago Marine Protected Area. Sea-level height anomaly and sea surface temperature were important foraging predictors at both sites, although birds experienced distinct environmental conditions between colonies. These results suggest that while brown boobies have colony-specific at-sea foraging areas, similarities in habitat drivers of distribution and foraging behaviour can inform predictions of distributions at other colonies within the archipelago, with important benefits for at-sea conservation efforts.

Evaluation of stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in marine organisms over time addresses how environmental variability (e.g., El Niño or The Blob) affects habitat use and food resources, respectively. This work focuses on the impact of warm events in the Northeastern Pacific Ocean on the foraging strategies of adult female northern elephant seals (Mirounga angustirostris; NES) from the San Benito Archipelago in Mexico during their post-molting migration, through isotopic variability in pups as maternal indicators. Analysis of δ¹⁵N and δ¹³C was carried out on lanugo samples (n = 311) of weaned pups from the 2013–2017, 2019, and 2022–2023 breeding seasons and correlations with sea surface temperature (SST) anomalies of the potential foraging areas of female NES from the San Benito Archipelago were investigated. Isotopic niches showed high overlap throughout most of the study period, suggesting a limited impact of SST anomalies on their foraging strategies. However, values of δ¹⁵N and δ¹³C differed in 2014, 2018, and 2021 relative to other years, suggesting shifts to distant regions in latitude and longitude, and increased foraging effort during the post-molting migrations of these warm years. Findings demonstrate the flexibility and adaptive capacity of female NES relative to the warm events of the last decade.

Floating materials of both natural and anthropogenic origin affect marine ecosystems and human economic activities. Although the tracking of floating materials is important to manage the economic risks, it is difficult to trace them back to the events of origin, such as tsunamis and underwater volcanic eruptions. The gooseneck barnacle Lepas anserifera, a rapid colonizer in pelagic environments, is a potential “natural logger” of floating materials. In this study, we performed temperature-controlled culture experiments and growth line staining in the laboratory to quantify the growth increments of shells (scutum and tergum) consisting the capitulum of L. anserifera separately, and to examine the effects of the temperature on their growth. Following calcein staining, the growth lines of L. anserifera were visualized under a fluorescent microscope, and gross (capitular length and width) and individual (scutum and tergum) shell growth were compared. Shells grew in twice as much in the capitular length direction than in the capitular width direction owing to the larger growth increases in the scutum than in the tergum. Growth increments were unaffected by temperatures in the range from 20°C to 30°C, although the growth appeared to slow down in September and October compared with August. The stable oxygen isotope composition (δ¹⁸O) of the shells represented the water temperature as previously known, and the present results showed that ¹⁸O enriched in scutum than tergum in most cases. Further understanding for the biomineralization process of barnacles is required for the precise application of environmental proxies in barnacle shells.

Understanding the drivers of morphological plasticity, a key mechanism allowing species to flourish under a range of conditions, can provide important information on how a species will adapt to climate-change. The kelp Ecklonia radiata is the dominant canopy-forming macroalgae in temperate Australasia, occurring across a wide environmental range. Previous assessments of morphological variation across Australasia have not included northeastern New Zealand (NENZ) populations, where E. radiata exhibits an anomalous long-stipe morphology. Morphology in NENZ E. radiata over nine locations was quantified to examine variability and its relationship with environmental drivers: depth, wave exposure, turbidity and temperature. Published literature was then reviewed to assess variation across Australasia in relation to similar large-scale environmental drivers. In NENZ, morphology was driven by depth, wave exposure, and turbidity, but not temperature. Thalli had short stipes and relatively long lamina at shallow depths (< 2 m) and across depths at highly wave exposed sites. Stipe length increased with depth and the long stipe morphology dominated deeper depths (4–12 m) at sheltered to moderately exposed sites. However, this relationship varied in relation to turbidity, with more turbid sites having shorter stipes across all depths. Regional variation in morphology across Australasia was most strongly related to wave climate rather than temperature with the long-stipe morphology characterising regions with low energy wave climates such as NENZ. This study highlights the high levels of variability in E. radiata morphology and its complex relationship with environmental stress. If Australasia’s wave climate is to increase in severity, our findings suggest morphological variability expressed across Australasian E. radiata populations will shrink.

Understanding the nutritional quality of macrozooplankton is crucial for elucidating energy and matter fluxes in marine food webs and their value as fish prey. This study examines the seasonal (winter, spring, summer) and spatial variability in three quality indicators -energy density (ED), polyunsaturated fatty acids (PUFA) content, and DHA/EPA ratio- of Euphausia spp. and Grimothea gregaria. These indicators were analyzed in relation to size and environmental variables (temperature, salinity, and chlorophyll-a concentration) in the San Jorge Gulf (45°–47°S, 65°30′-67°30ʹW; Southwest Atlantic Ocean), a key feeding ground for commercially important fish on the Argentine shelf. Results showed that ED increased with size in Euphausia spp. but decreased in G. gregaria. Seasonal changes were the primary drivers of variations in the nutritional quality, with PUFA content being the index most contributing. For both species, the highest mean PUFA content occurred in winter and the lowest in summer, an inverse pattern to ED. The DHA/EPA ratio also peaked in winter and dropped in spring. Species differences significantly affected PUFA content and the DHA/EPA ratio, with Euphausia spp. exhibiting higher values. Although environmental variables, particularly bottom temperature and chlorophyll-a, varied significantly across sampling areas, no clear spatial patterns emerged in the quality indicators, likely due to the limited sample size. These results provide new and baseline information of zooplankton that can clarify the trophic interactions of many fish and their respective predators along the Argentinean Shelf, and how these relationships may change with environmental variability in the current global change context.

Aurelia is a genus of scyphozoan jellyfish with cosmopolitan distribution and a propensity to form large aggregations, or “blooms.” Along the northern Gulf of Mexico (GoM) coast, blooms of Aurelia have caused problems for human enterprise. Mature Aurelia sp. 9 and sp. 18 medusae are observed each season, yet their benthic originators, the polyps, have never been found in nature in the GoM. The absence of information on polyp locations greatly limits our understanding of bloom formation, as we are unable to identify bloom origins or study medusae production in situ. To address the lack of knowledge on polyp distribution, suitable habitats, including natural and artificial settlement substrates for A. sp. 9 and A. sp. 18 were modeled using a GIS spatial analysis, utilizing previously published experimentally derived species’ tolerance ranges for temperature and salinity. Spatial models considered temperature and salinity parameters from surface down to 1500 m utilizing a ¼ degree grid size. The results suggest the GoM coastal waters have suitable environmental parameters for A. sp. 9 but not A. sp. 18 and that water temperature, but not salinity, limits the distribution of both species. Also, 94% of GoM artificial reefs and 97% of gas platforms fell within the modeled distribution range for A. sp. 9, compared to only 37% and 40% for A. sp. 18, respectively. Models suggest that A. sp. 18 may be an offshore species restricted to the deeper shelf waters of the GoM by summer-high water temperatures and that future increases in water temperature, such as those expected with climate change, may negatively impact Aurelia jellyfish populations in the northern GoM.

Coral reef degradation is a worldwide and growing phenomenon triggering habitat transformation from live to dead coral fragments. Macroinvertebrates play key functions in coral reefs, yet research on the size distribution of their community attributes is limited, particularly in the Eastern Tropical Pacific (ETP). We assessed the size distribution of the macroinvertebrate communities in live and dead corals in an ETP coral reef off Colombia. Live coral supported greater macroinvertebrate biomass than dead corals. In live coral, > 90% of total biomass was allocated in the > 8 mm class, which was mostly represented by trapeziid crabs and alpheid shrimps, both obligate symbionts of Pocillopora colonies. No differences were found in macroinvertebrate densities between substrates. Macroinvertebrate communities were dominated by crustaceans, though not in every size class. In live coral, Decapoda dominated in all size classes except 0.5–1 mm, which was the only class where dominance of a single taxon was not observed. In dead corals, the dominance of crustaceans was only observed in the 0.5–1 mm class due to high abundances of tanaidaceans. The remaining size classes were dominated by Polychaeta (1–2 mm, 2–4 mm) and Ophiuroidea (4–8 mm, > 8 mm). Our findings highlight that coral degradation events could lead to macroinvertebrate assemblages with lower biomass contributions, higher proportions of small crustaceans (< 1 mm), and taxonomic shifts. Such transitions from live to dead corals could likely impact food-web interactions between macroinvertebrates and higher trophic levels, potentially altering the ecosystem services offered by coral reefs.

Anthropogenic disturbances are having strong, negative effects on aquatic systems globally, altering ecological communities and potentially creating vacant niches for both native and non-native species (NNS). Globalization and new trade routes have amplified the spread and establishment of NNS by connecting disturbed areas worldwide. In this study, we conducted a comparative assessment of seasonal variations in amphipod communities at three southeastern Baltic Sea locations – two anthropogenically impacted and one protected habitat – to determine if native and NNS diversity differed among these habitats. Our study revealed nine amphipod species - of which two were NNS - across all three habitats. The impacted habitats had significantly higher native species richness and lower NNS abundance. Grandidierella japonica was the only NNS found at the impacted habitas. In the case of the protected habitat, NNS Gammarus tigrinus was dominant for most of the year. In autumn, dominance shifted in favour of the native Gammarus locusta and Microdeutopus cf. gryllotalpa. Grandidierella japonica was not detected there. Although anthropogenically impacted habitats may be under higher invasion risk, other environmental factors, such as salinity and temperature, may be driving the establishment pattern of NNS and the resulting community structures. Furthermore, undisturbed and/or protected habitats may be highly vulnerable to invasions due to more tolerable environmental conditions, robust NNS populations and naïve native species to newcomers. Seasonality is an important aspect of ecological studies and must be taken into account, as omissions could potentially distort our understanding of the dynamics of ecosystems and prevent the detection of NNS.