Marine Biology最新文献

The paper explores the dynamic relationship between sharksuckers and Atlantic Nurse sharks within a fish cleaning station in South Eleuthera, The Bahamas. Despite the prevalent symbiotic association between echeneid fishes and sharks, the specifics of their interactions, behavioral adaptations, and the influence of food availability remain understudied. The research employed a comprehensive observational approach, focusing on free-swimming and attached sharksucker’ behaviors (Echeneis spp.) in the presence of Atlantic Nurse sharks. Through a month-long study, both qualitative and quantitative analyses of the behaviors were conducted. The results challenge the traditional perception of a purely mutualistic or parasitic relationship, suggesting a more complex dynamic between sharksuckers and sharks. Specifically, the study indicates an increase in boldness and competitive behaviors towards sharks in a controlled feeding setting, indicating that sharksuckers’ behaviors and relationships with their hosts are constantly evolving and should not be treated as simply symbiotic.

Coral reef fishes are usually assumed to be most strongly associated with reef-building corals. However, sponges can be a significant structural component of coral reef ecosystems and their framework can enhance the local abundance and biodiversity of fish assemblages. Little is known regarding the range of fish species using complex sponges as either shelter or feeding substrata. Here we use a combination of stationary video cameras and focal animal sampling to document fish species positively associated with complex sponges in Kimbe Bay, Papua New Guinea. Stationary cameras identified 45 fish species using the sponges for either shelter, feeding substrata or as sites for ambush predation. A guild of 10 individual fish species from five families (Blenniidae, Chaetodontidae, Gobiidae, Labridae and Pomacentridae) were observed to quantify sponge and other habitat use and compared with habitat availability to determine the level of sponge selectivity. One species, Pleurosicya elongata (the Slender Spongegoby), lived in obligate association with Ianthella basta (Elephant Ear sponge), and there was a positive relationship between sponge size and number of resident fish, however this was not significant for all life stages. Five other fish species appeared to preferentially select sponges as habitat (Amblyglyphidodon aureus, Chaetodon kleinii, Coradion chrysozonus, Escenius prooculis and Pomacentrus nigromanus), while for others, sponge use appeared incidental. When selectivity indices were calculated for specific sponge species it was apparent that some fishes exhibited preferences for particular sponge species or growth forms. These results suggest more fish species may be reliant on sponges than is widely appreciated.

Reef manta rays (Mobula alfredi) face threats from human exploitation and activity in several regions of the world and crucial information on the ecology of the species is needed. The species is observed at several sites in all parts of the archipelago of New Caledonia where anthropogenic influence is presumed to be minimal. This study is the first to investigate the population of New Caledonia and focuses on its characteristics and its habitat use. Photographs of reef manta rays were collected directly from the authors (14.4%) between 2017 and 2020 and gathered from recreational divers and snorkelers (85.6%) from 11 sites around New Caledonia. The authors used the unique ventral coloration patterns of the manta rays that were clearly identifiable from 1741 of these photographs to identify 391 individuals and record their physical characteristics (sex, injuries, and colour morph) and resighting rates. These results highlight the widespread distribution of the species in the archipelago (11 sites) with little connectivity between all aggregations sites, with only 5.4% of the individuals observed at more than one site. Strong and long-term site fidelity was recorded at all studied sites through re-sighting rates (52.2% overall) and residency analysis. The population also records the world highest known proportion of melanistic manta rays (43%) to date, and a balanced male: female ratio (1.0:1.15). The analysis of injuries reported that 44.8% of all reef manta rays identified (n = 391) had noticeable wounds or injuries with no significant difference in the proportions of males and females injured. From these injured individuals only 9.8% of injuries judged to be of anthropogenic origin and 29.7% from attempted predation. Our study complements and correlates previous findings on this population that revealed strong site fidelity and low connectivity. The different characteristics of this population of reef manta rays also emphasize that concerns about species in New Caledonia are limited and that such favourable context needs to be preserved as reference for conservation.

In recent years, population outbreaks of the annelid Hermodice carunculata (Polychaeta, Amphinomidae) are recurrently detected along the coastal zone of the Salento peninsula (Southern Italy), with impacts on marine benthic ecosystems. Annelida are renowned for their remarkable regeneration potential, enabling them to reform lost body parts. A handful of studies have reported posterior regeneration of H. carunculata, but anterior regeneration has not been fully explored. In this study, we investigated the capacity of H. carunculata collected in shallow coastal areas (Ionian Sea, 40°08’26.9” N 17°58’44.1” E) to regenerate anterior body parts under different temperature conditions (22 and 14 °C) and considering two different body sizes (∼ 4 g and 25 g). In addition, histological analysis and lipid analyses were carried out to detect changes in the reproductive cycle and lipid storage during ongoing regeneration. The results suggest that small and large-sized specimens of H. carunculata can regenerate efficiently anterior body parts in 12–20 weeks post amputation when kept at 22 °C. Small-sized worms kept at 14 °C regenerated slower but died in 24 weeks post amputation before regenerating a mouth, while large-sized worms kept at 14 °C were affected by a 100% mortality during blastema formation. In addition, lipid extraction analyses show that H. carunculata can regenerate during extended periods of starvation by de novo synthesizing lipid reserves and regeneration in H. carunculata does not negatively impact the reproductive cycle, as gametogenesis occurs also during the regenerative processes.

The growth properties and environmental adaptability of different corals and symbionts vary. Therefore, insights from the adaptive mechanisms of Symbiodiniaceae in corals are very meaningful. In this study, we surveyed the seawater characteristics at three sites on Luhuitou fringing reef, Hainan Island (China), sampling three native corals Pocillopora damicornis, Acropora hyacinthus, and Galaxea fascicularis on 27 September 2021. The photo-physiological (Fv/Fm, Y(II), α, and rETR) were measured, and high-throughput sequencing of Symbiodiniaceae ITS was performed. The Luhuitou site had the lowest temperature (28.845 °C ± 0.01), salinity (33.967 ± 0.03), and pH (8.468 ± 0.05) among the three sites. The Sanya site contained significantly the highest ammonium (7.406 μmol/L ± 1, P < 0.05). The nitrate of the Xiaozhou site was 1.5 times significantly higher than the other two sites. Three corals and their Symbiodiniaceae were adapted differently. P. damicornis showed more plasticity and was dominant by Cladocopium sp. C1d at high-ammonium habitat. A. hyacinthus was dominated by Cladocopium (C3 and C1232) and they had the lowest Fv/Fm (0.595 ± 0.02) in poor integrated water quality environments (the Xiaozhou site) among three corals, suggesting that the less adaptation. G. fascicularis established a stable symbiotic relationship with Durusidinium sp. D1, and they had a more stable symbiotic system and were better suited for long-term reef restoration. Our results provide a deeper understanding of the environmental adaptations of three corals at the Luhuitou fringing reef. Meanwhile, it provides a perspective application for coral transplantation species selection in restoring local reef ecology in the future.

Mapping spatial variation in stable isotope values (isoscapes) of primary producers and consumers can provide insight into regional patterns of biogeochemistry and be used to trace the movements of mobile animals. Here we present carbon (δ¹³C) and nitrogen (δ¹⁵N) isoscapes for an expansive region of the continental United States (Mid Atlantic Bight to the NW Gulf of Mexico) derived from inshore lizardfish (Synodus foetens) and explore temporal stability and environmental drivers of observed isotopic variation. We observed significant spatial variation in lizardfish δ¹³C and δ¹⁵N values throughout much of the Atlantic and Gulf coasts, reflecting local biogeochemistry regimes. Extensive sampling throughout the northern Gulf of Mexico (NGOM) revealed positive relationships between lizardfish δ¹³C values and bottom temperature, likely reflecting lower carbon isotope discrimination between CO₂ and phytoplankton in highly productive, warm, inshore environments. Conversely, δ¹⁵N values were not well explained by environmental parameters, but appeared higher in nearshore environments of the NGOM, which are heavily influenced by nitrogenous run-off from land. An isotopically unique region of high δ¹³C values and low δ¹⁵N values were observed for lizardfish sampled in the Eastern NGOM off the southwest coast of Florida, reflecting a potential influence of seagrass and/or macroalgal productivity supporting the base of the food web. Overall, these findings underscore the utility of benthic lizardfish stable isotopes for inferring local patterns of ocean biogeochemistry throughout expansive ocean environments. In application, these data can be used to define migratory histories of mobile taxa and support contemporary critical habitat assessments.

Understanding spatial heterogeneity in reproductive success among at-risk populations facing localised threats is key for conservation. Sea turtle populations often concentrate at one nesting site, diverting conservation efforts from adjacent smaller rookeries. Poilão Island, Bijagós Archipelago, Guinea-Bissau, is a notable rookery for green turtles Chelonia mydas within the João Vieira-Poilão Marine National Park, surrounded by three islands (Cavalos, Meio and João Vieira), with lower nesting activity. Poilão’s nesting suitability may decrease due to turtle population growth and sea level rise, exacerbating already high nest density. As the potential usage of secondary sites may arise, we assessed green turtle clutch survival and related threats in Poilão and its neighbouring islands. High nest density on Poilão leads to high clutch destruction by later turtles, resulting in surplus eggs on the beach surface and consequently low clutch predation (4.0%, n = 69, 2000). Here, the overall mean hatching success estimated was 67.9 ± 36.7% (n = 631, 2015–2022), contrasting with a significantly lower value on Meio in 2019 (11.9 ± 23.6%, n = 21), where clutch predation was high (83.7%, n = 98). Moderate to high clutch predation was also observed on Cavalos (36.0%, n = 64) and João Vieira (76.0%, n = 175). Cavalos and Meio likely face higher clutch flooding compared to Poilão. These findings, alongside observations of turtle exchanges between islands, may suggest a source-sink dynamic, where low reproductive output sink habitats (neighbouring islands) are utilized by migrants from Poilão (source), which currently offers the best conditions for clutch survival.

Foraging animals move through the environment to satisfy their requirements for food, rest, reproduction and risk-avoidance. Understanding how animals respond to changing environmental conditions can help to characterise favourable habitat and determine whether they might be motivated to depart when those habitats become unsuitable. Foraging green turtles are typically residents that scarcely move in response to environmental changes or disturbances. Some individuals though, exhibit high mobility at fine scales. We developed an analysis of Fastloc GPS tracks of 61 green turtles using cox regression models and generalised linear mixed models to investigate the influence of a suite of environmental characteristics on the length of residence time and probability of turtles transitioning between two behavioural modes, “stay” or “go”. Decisions to move (“go”) were influenced by short-term changes in the local environmental conditions. Individuals were more likely to “stay” when temperature increased during their stay and were more likely to “go” when turbidity decreased, and they entered deeper habitats. This result implies that foraging and resting (“staying”) primarily occurs in benthic, shallow, warm habitats, while transit (“going”) is facilitated in deeper, clear water. We also determined that individuals within the green turtle foraging aggregation respond differently to environmental cues to move and hypothesise that a diversity of strategies within a foraging aggregation could confer its resilience to disturbance events. Our study provides new evidence of the factors influencing movements in green turtles and can aid in predicting how they may respond to future changes and enhance risk mitigation efforts through dynamic and adaptive planning.

In both terrestrial and marine ecosystems, prey species exhibit various reactions to predators, including avoidance, fighting and freezing. Acoustic communication associated with mobbing has been depicted in numerous tetrapod species. This sonic behaviour remains however largely unknown in fish although mobbing has been shown in different coral reef fish as a response to predation risk. This study focused on the communication strategy of prey species in the presence of predators. We tested the reaction of the holocentrid Sargocentron caudimaculatum when facing a moray eel and compared the sounds they produced against the predator with sounds produced when the fish are hand-held, recorded in standardized conditions. When introduced in mesocosms to a moray eel, S. caudimaculatum produced distinct distress sounds, resembling staccato calls, and swam towards the predator with their heads pointed in its direction and their dorsal fin erected. This observation supports a mobbing behaviour with specimens shifting from an escape behaviour to an aggressive response in presence of predator. Moreover, these sounds are different from those emitted during manual handling. This difference in acoustic signal suggests the coexistence of multiple warning/alarm sounds in this species. Holocentrids can produce different kinds of sounds witnessing their ability to provide graded information based on the perceived predation risk. We suggest that species of this family would be a suitable and promising group with which to test the hypothesis of acoustic coordination where individuals could inform their conspecifics about an increase in the immediate predation risk through appropriate alarm calls and trigger an escape response of the group if needed.

Seagrass beds are ecologically and economically important coastal ecosystems, and seagrass-associated organisms are a key part of their biodiversity. Marine organisms that reproduce through broadcast spawning are likely to have less genetic differentiation among populations than those that use other modes of reproduction, but this has not been well studied. Here, we investigated the genetic diversity, genetic differentiation, and migration patterns of the seagrass-associated sea star Protoreaster nodosus across 12 sites spanning approximately 2500 km from the Ryukyu Archipelago, Japan, to the Philippines. We genotyped 405 individuals by using seven microsatellite loci and analyzed allelic richness and expected heterozygosity as indices of genetic diversity. Of these two indices, only expected heterozygosity decreased slightly with increasing latitude. These results suggest that genetic diversity has not clearly decreased, even in the isolated Ryukyu Archipelago populations. Geographic distance was significantly correlated with genetic differentiation (pairwise F_ST: − 0.005 to 0.049). However, populations in the Ryukyu Archipelago and the Philippines showed relatively low genetic structuring and the pairwise genetic differentiation between these regions was often non-significant. Analysis of historical migration rates showed bidirectional north–south migration, which appears to be influenced by the Kuroshio Current and its countercurrents.