Marine Biology最新文献

Wedgefishes have recently been recognised as one of the most imperilled marine fish families worldwide. However, many knowledge gaps about their biology and ecology hinder conservation efforts. Here we used a combination of acoustic telemetry and acceleration datalogger technology to gain fundamental insights into the fine-scale behaviour, habitat use, size of activity spaces, and residency of adult female bottlenose wedgefish (Rhynchobatus australiae) in the Ningaloo region of northwestern Australia. Acoustic tracking data over one year demonstrated that female bottlenose wedgefish continuously resided in a relatively small area of a productive coral reef lagoon. Acceleration data revealed that bottlenose wedgefish were nocturnal, with time of day having a greater influence on activity than tidal patterns. Bottlenose wedgefish also increased activity with seasonally increasing temperatures. We identified several discrete behavioural signatures in the acceleration data, inferred to correspond to chafing, settling/burying behaviour, foraging behaviour, and escape behaviour, based on their kinematics. Further observations are required to confirm these behaviours with certainty. Additionally, according to datalogger and acoustic data, tagged bottlenose wedgefish rarely inhabited areas greater than 2 m deep. Together, these first insights into behaviour and habitat use of adult female bottlenose wedgefish highlight the importance of nearshore habitats for this species and indicate that they may be highly resident to specific areas. Our findings provide important insight into the conservation of bottlenose wedgefish in northwestern Australia, including potential effectiveness of protected areas and interactions with specific anthropogenic threats such as shoreline development and recreational beach fishing.

Aggregations and social interactions play an important role in the movement ecology of many animals, including elasmobranchs. Several of these species have shown the capability of carrying out complex social behaviours, and the importance of sociality in this taxon is being realized. Although it is a growing field of study in the case of these organisms, these processes still need to be better understood, especially to support management and conservation policies. In this study, a long-term acoustic telemetry data set collected on Dasyatis pastinaca in a coastal marine protected area was analysed. A co-occurrence network analysis was done to investigate preferential associations among individuals, revealing non-random associations among them. The analysis revealed a few strong and consistent associations that were maintained across inter-migratory periods, as this species performs seasonal migrations to a nearby estuary, suggesting temporal stability of the observed associations. Moreover, individuals had similar average positions and a generally high overlap of space use in both periods, indicating some level of site fidelity to the fully protected area. Groups of up to 64% of tagged individuals were co-detected at a same receiver, particularly in the western side of the array. Despite our limited sample size, likely underestimating associations, these results show that in addition to their large-scale movement pattern, D. pastinaca is likely to also present active partner preference and spatial structure at a finer spatial scale. The nature of such results is relevant to support the protection of these species.

The Antarctic benthos is rich in biodiversity, with many species being endemic to the Southern Ocean. Multiple factors such as oceanic currents, glacial cycles and reproductive life stages have been attributed to the distribution of benthic dwelling invertebrates around the continent. The sea spider (Pycnogonida) Nymphon australe is a paternal brooder, which lacks a pelagic planktonic life stage. Typically brooding is assumed to suggest limited dispersal capabilities. Here we investigated the genetic structure of N. australe, a highly abundant pycnogonid species in the Southern Ocean to test assumptions of a documented circumpolar distribution. Previous studies with mitochondrial data have revealed that N. australe has high genetic diversity, limited gene flow, as well as distinct geographic structure. To resolve the phylogeographic structure of the circumpolar N. australe from the Antarctic continental shelf, we used 3RAD single nucleotide polymorphism (SNP) data from 111 individuals sampled from ten different, circumpolar geographic regions including the Western Antarctic Peninsula, Ross Sea, Weddell Sea, and Eastern Antarctica. Analyses revealed populations to have distinct regional populations with strong geographic structuring observed by locality and suggest the possibility that N. australe may be a species complex in the Southern Ocean.

Understanding how population structure and demography are determined is a central theme in marine biogeography. While historical events, such as past climate change, are important determinants, the mechanisms by which they act are not well understood in many marine species. In this study, the population structure of the Japanese, marine intertidal gastropod Lunella correensis was investigated to determine whether it has been affected by past environmental changes. A genome-wide SNP analysis, L. correensis showed a genetic gradient along the coast and a weak genetic differentiation between sites in the Sea of Japan and the Pacific Ocean. Demographic inference suggests that the effective population size expanded and shrunk in response to periods of rapid warming and cooling due to past climate change. Further, ecological niche modelling suggests that the population size of L. correensis increased by advancing into the Sea of Japan during rapid warming after the Last Glacial Maximum. Notably, our analyses suggest that recent human activities may have influenced the effective population size of this species. Specifically, the period of reduction in the population size coincides with environmental changes and habitat loss associated with development along the Japanese coastal area. Thus, these results emphasize that the genetic structure and demography of marine species have been influenced by past environmental change around the Japanese Archipelago.

Accurately quantifying primary productivity in highly dynamic subtidal rocky habitats, particularly those with high canopy-forming macroalgae, is inherently challenging, leading to a scarcity of information. Kelp primary productivity has primarily been assessed through (1) quantification of carbon standing stock and biomass, which provides limited information on rates of primary productivity; (2) ex-situ incubations in the laboratory, in which the obtained values may not represent the actual productivity of a community; and (3) in-situ incubations in detached plants or including only the fronds. To address this issue, we describe a versatile methodology—the Benthic Incubation Chamber (BIC); and tested it along the morphologically diverse Portuguese continental coast. BIC is designed to assess in-situ primary productivity in a variety of benthic communities (high and low canopy), fulfilling the existing need to measure productivity in highly dynamic, shallow subtidal habitats. The method involves incubation chambers where total oxygen flux, temperature, and photosynthetically active radiation (PAR) are simultaneously recorded. From those measurements, Net Community Productivity (NCP) and community respiration (CR) for a given biomass and water volume were derived for each chamber. Incubations performed in the Portuguese continental coast demonstrated the feasibility of this technique to obtain reliable in-situ net primary productivity values in a range of subtidal habitats. This method contributes to a comprehensive approach to sustaining and protecting vital marine ecosystems, supporting biodiversity and addressing environmental issues.

Southern Ocean zooplankton provide globally significant ecosystem services through their role in carbon sequestration, nutrient cycling and food webs. However, the remote and extreme nature of the Southern Ocean creates significant logistical difficulties for studying zooplankton all year round. Here, for the first time in the Southern Ocean, we present the seasonal occurrence of the zooplankton assemblage in the Northeast Scotia Sea using a sediment trap deployed throughout 2018 (P3 observation site, 52.80˚ S, 40.14˚ W). Results show that copepods and pteropods dominated trap abundance, representing 25.0–68.3% and 13.4–72.5% respectively, followed by amphipods (1.0–7.2%) and hydrozoa (0.2–15.6%). The dominant signal in copepods was consistent with previous observations using traditional (net) sampling methods while the relative contribution of pteropods, amphipods and hydrozoa was increased in our trap. Further, zooplankton showed taxon-specific seasonal signals, with a relatively high number of individuals throughout winter, including an increase in hydrozoa occurrences. This observation highlights the importance of zooplankton as source of nutrition for the benthic community in the winter. Our data reiterate the utility of sediment traps for observing zooplankton in remote locations and sampling specific taxa that might be otherwise understudied.

Inhabitants of rocky intertidal shores, including gastropods, require specific adaptations to cope with numerous challenges that vary across the intertidal levels. We collected Stramonita biserialis snails from upper (wave-protected and intense predation) and lower (wave-exposed and low predation) intertidal sites to compare the following traits: shell skeleton (ventral and abaxial lateral views of shell shape, thickness, and mass), foot size, energy metabolism, and attachment strength to determine whether the trait values of snails from each zone fit the environmental challenges they face. We used a Principal Component Analysis to reduce the dimensionality of the data. Multivariate Analysis of Covariance (MANCOVA) for comparing characteristics between the two intertidal zones, and Partial Least Squares (PLS) analyses for testing the integration of overall snail characteristics. The traits of the snails of the two intertidal sites matched with the adaptations expected to allow them to cope with their contrasting challenges. The snails from the lower intertidal had more streamlined shells (which reduces drag forces) and a larger aperture and foot extension (which increase the strength of their attachment to the substrate) compared to snails from the upper sites. Snails from the lower intertidal also had a high mass-specific metabolism and soft body proportion, indicating that these snails from the wave-exposed sites have an energetically active musculature that matches their strong substrate attachment. The thin shell walls of the snails of the lower intertidal match the relatively low predatory pressure there.

Little is known about the post-nesting migration and foraging areas of hawksbill turtles (Eretmochelys imbricata) nesting on St. Kitts and Nevis, an important nesting site for hawksbills in the eastern Caribbean. To elucidate internesting, migration and foraging patterns of hawksbills from Nevis, we satellite tagged 28 post-nesting turtles between 2006 and 2022. Internesting, migrating and foraging activity periods were determined using a switching state–space model to estimate the behavioral state of the turtle’s locations. Twenty-five turtles (83–2,171 tracking days) established a foraging area, migrating between 5.3 and 2,799.5 km from the nesting beach. Twenty-one turtles were tracked during internesting movements with internesting areas ranging between 1.9 and 28.2 km². Nearly half of the internesting centroids were located closer to a different beach than the beach where the turtle was originally encountered nesting. Hawksbills crossed through 29 different Exclusive Economic Zones (EEZs), including zones with legal sea turtle fisheries or traditional subsistence use. Core foraging areas (KDE 50%) ranged between 3.8 and 69.0 km². Nearly a third of foraging centroids were within a Marine Protected Area (MPA), while nearly a quarter were within a legal sea turtle fishery EEZ. Hawksbills nesting on Nevis disperse to local, regional, and Caribbean wide foraging grounds, emphasizing the necessity of cooperative efforts to protect turtles and their habitats to ensure support of the recovery of hawksbill turtles throughout the wider Caribbean.

Geographic isolation is a factor that is known to affect species composition and diversity in marine systems. In this study, we tested the effects of geographic isolation on invertebrate fauna living among the belt-forming foundation species Fucus vesiculosus in the northern Baltic Sea. Sampling was carried out on reefs with varying levels of isolation (0.5, 1 and 2 km) in July 2021 in the Åland islands (between 59.96°N 20.24°E and 59.75°N 20.84°E). The total number of taxa, abundance, Shannon-Wiener index, Pielou’s evenness and biomass were calculated and the effects of isolation were tested using generalised linear models. Multivariate methods were used to analyse differences in the invertebrate community composition. Although the number of taxa and Shannon´s diversity index did not vary along the isolation gradient, the total abundance of fauna decreased with increasing isolation. In addition, some taxa-specific patterns were observed, e.g. the abundance of insect larvae decreased with isolation while isopods were more numerous in the most isolated locations. As diversity and the number of taxa were similar regardless of isolation, shallow Fucus vesiculosus belts likely act as important biodiversity refuges and potential stepping-stones for invertebrates in remote outer archipelago areas. In a changing climate, these kinds of refuges aiding species dispersal are likely to be even more important, and should be considered in conservation planning.

In eutrophied marine systems such as the Baltic Sea, diazotrophic cyanobacteria have the potential to add additional bioavailable nitrogen (N) to the system through fixation of atmospheric dinitrogen (N₂). However, their growth is regarded to be limited by phosphorus availability (P). This study investigates the response of two cyanobacteria species, Aphanizomenon flosaquae and Nodularia spumigena, collected from the Gulf of Riga under different environmental conditions to a short-period dissolved inorganic phosphorus (DIP) enrichment. The samples were collected during the summer cyanobacterial bloom of 2022 in the central region of the Gulf of Riga. Contrary to expectations, neither species demonstrated a significant increase in biomass. The study also established that N₂-fixation rates did not correlate directly with the total diazotrophic cyanobacteria biomass, but showed a significant correlation with heterocyst presence in both species addressed during this study. The findings suggest the influence of additional factors beyond DIP availability on the N₂-fixing cyanobacteria growth in the Gulf of Riga.