Marine Ecology-An Evolutionary Perspective最新文献

The Spratly Islands are a remote group of more than 150 coral reefs and islands scattered in the south-central South China Sea and representing a biodiversity hotspot in the region. An integrative anthropogenic impact and increased frequency of thermal anomalies have increasingly been threatening these unique reef ecosystems over the last three decades. The repetitive surveys conducted on four coral reef sites within the Spratly Islands in 2018–2019 and in 2021 revealed a significant decrease of coral cover, particularly of acroporids, a decrease of species diversity and an outbreak of crown-of-thorns starfish (COTS) Acanthaster planci (the variation of starfish abundance was 1–18 starfish/100 m²). Moreover, one of two additional sites, located within the same study reefs, revealed a coral-killing photoautotrophic cyanosponge Terpios hoshinota, covering 56.9% of all dead scleractinian colonies on the reef slope of this site. Analysis of sea surface temperature dynamics during the last 4 years (2018–2021) in the Spratly area allowed suggesting the concurrent negative effect of the COTS outbreak and the thermal anomaly of 2020 on local coral communities. This effect may have contributed to the general trends in coral reef decline in the area of the Spratly archipelago under the condition of repetitive thermal stress and increasing anthropogenic impact.

The impact of the introduced red king crab (RKC), Paralithodes camtschaticus, in the Barents Sea was mostly studied through its direct predation on native species. This study uses stable isotope analysis of carbon and nitrogen to characterize major trophic groups (including grazing sea urchins) and specifically looks at RKC's trophic position and niche partitioning with the native hermit and spider crab species. To achieve this, we sampled organisms from the food web of a small fjord-like Zelenaya Inlet on the Murmansk coast in the southwestern Barents Sea and the open sea coast, just outside the inlet for comparison. There, macrophyte-derived carbon is the major source of organic matter along with the phytoplankton. In general, the fucoid source of primary production was more prominent within the inlet food web compared to the nearby open coastal zone. Isotopic trophic niches calculated using SIBER analysis showed partition between the native hermit and spider crabs suggesting, some degree of trophic segregation between coevolved species. RKCs are clustered together in the center of native decapod species' niches. There were some distinct differences between the feeding habits of RKCs within the inlet and the open sea coastal waters. The subadult RKCs that are present in the inlet throughout the year have a narrower (in the area and specifically in δ¹⁵N dimension) niche than the adults from the open sea. The latter have a wider variety of food items due to their migration and may prey on food items from different trophic levels. Sea urchins are an important trophic link transferring the macrophyte carbon to RKC. However, P. camtschaticus may also directly consume plant residues. Despite generally similar calculated trophic levels of decapod species, our isotopic data and literature data on the food composition of Paralithodes camtschaticus in the Barents Sea do not indicate significant RKC's competition with, and predation on, native species of crabs.

The maintenance of high diversity in deep-sea sediments is often hypothesized to be a result of heterogeneity in disturbance and carbon availability creating long-lived patches of unique communities. Deep-sea food falls are known to contribute to this patchiness, influencing the beta-diversity of soft-bottom communities through varying effects of enrichment and disturbance. Previous food fall work has centered on large (>1000 kg, e.g., whales) or small (0–10 kg, e.g., kelp, fish, wood) food parcels, leading to the hypothesis that only the largest persist long enough to impact sediment communities. The effect of intermediately sized (10–1000 kg) carcasses on sediment macrofauna communities remains poorly understood. Here, we deployed an individual Alligator mississippiensis carcass (19.5 kg) as organic enrichment to an otherwise food-poor landscape at 2034 m in the northern Gulf of Mexico. Sediment cores collected at three distances from the alligator fall following decomposition were used to describe changes in macrofauna abundance and alpha- and beta-diversity. We found that the carcass enriched nearby sediments with up to three times more carbon than background sediments. This carbon enrichment near the carcass did not influence species richness but did correlate with higher abundance and a suite of species unique from background communities. Our findings suggest that the food fall size threshold above which enrichment of local sediments occurs may be lower than previously thought, as we demonstrate that an intermediately sized (19.5 kg) food fall can contribute carbon and promote beta- and thus gamma- diversity of the infaunal benthos.

Elysiais a genus of sea slugs in which some species can “steal” chloroplasts (kleptoplasty) from algae and keep them photosynthetically active inside their cells. Solar-powered animals are more susceptible to climate change as photosynthesis can increase the stress for these animals in extreme environmental conditions. Here, we used the Maxent algorithm and environmental envelopes (i.e. the multi-dimensional environmental space in which a species can occur) to model the ecological niche of 21 Elysia species in the Caribbean to estimate their current and future potential distribution. We then used predicted distributions to map potential taxonomical richness and to describe the representation of the genus inside the marine protected areas (MPAs). For most species, we show an expansion of the northern and southern range of distribution, but a reduction in the central part. Although changes in richness appeared in different areas, predictions emphasize four large extensions that have a potential current richness of 13 and will have no species in the future: Pamlico Sound, North Carolina; the southwest of the Gulf of Mexico; the Great Bahama Bank; and the southwest of Brazil. Out of the total area with environmental conditions adequate for at least one of the species in the genus, 24.7% is located within MPAs.

Ecopath model is a snapshot of a particular ecosystem at a time to quickly reflect the real-time status, characteristics and nutritional relationships of remaining systems in the water. Based on Aoshan Bay fishery resource data collected in 2006, 2013 and 2018, Ecopath models of the Aoshan Bay ecosystem were constructed for these 3 years using EwE 6.6 software. The models of the Aoshan Bay ecosystem included 15 functional groups. Based on the 3 models, we compared and analysed changes in ecosystem structure and phylogenetic characteristics. The trophic interactions between the 15 functional groups were aggregated within four effective trophic levels at 2006, 2013 and 2018. Most of the functional groups were laid within the trophic levels TL 2 and TL 3. The average trophic levels in 2006, 2013 and 2018 were 2.318, 2.444 and 2.410, respectively. The calculated ecotrophic efficiency (EE) value for this ecosystem was highest for Zooplankton (EE = 0.898, 2006), Nibea albiflora (EE = 0.857, 2013) and other demersal fishes (EE = 0.963, 2018). In this study, the calculated TPP/TR was 4.572 (2006), 4.484(2013), 5.347(2018), which indicates the ecosystem is in a developmental stage (not fully mature), the highest mature ecosystem is 2013 and gradually decrease in 2018. In 2013, the FCI is 4.814 and higher ecosystem's maturity than 2006 and 2018, indicating high utilization of primary productivity and detritus. Through analysis of Ecopath models for different years, the characteristics of ecosystem changes in the Aoshan Bay over the past decade were revealed, indicating that the Aoshan Bay ecosystem is still in an unstable and immature state, which provides scientific reference materials for the restoration of fishery resources in this sea area.

Most organisms reproduce seasonally, including most species of marine invertebrates that live across wide ranges in habitat, depth and environmental conditions. We asked: What ultimately selects for seasonal reproduction in benthic marine invertebrates with planktotrophic larvae (characteristic of ≥70% of marine invertebrates)? We hypothesized that seasonal variation in food available for the larvae ultimately selects for timing of adult reproduction. Testing this hypothesis requires a whole life cycle perspective and approach. Using a known proximate cue, daylength, we shifted gametogenesis in the laboratory by six months in a seasonally breeding temperate sea star, the Ochre Star Pisaster ochraceus (Brandt 1835). We were then able to induce spawning, fertilize gametes and culture resulting embryos in vitro to produce feeding larvae six months out of phase with natural photoperiod. We field-reared these out-of-season larvae, similarly produced in-season conspecifics and similar larvae of an aseasonally breeding asteroid, the Bat Star Patiria miniata (Brandt 1835) in mesh-covered flow-through containers that were deployed in seasonally contrasting oceanographic conditions reflecting different productivity regimes and larval food availability in spring and fall. Larval development and survival were similar between seasons: for example, planktonic larval duration was 48 d to first metamorphosis in spring vs. 45 d in fall for P. ochraceus. Hence, temporal variation in available phytoplankton may not be an ultimate selection factor acting on these larvae to regulate timing of seasonal reproduction in the adults. Alternatively, in this and other species of marine invertebrates, selection acting on early benthic juveniles or other life stages may determine the timing of adult reproduction.

Movement studies on marine animals can inform conservation and fishery management planning through data that explain likely dispersals and home-ranging behaviours. Relatively few studies are documented for exploited marine invertebrates, despite many having a high ecological and commercial value. We assessed the diurnal movement patterns of Thelenota ananas and Thelenota anax, the world's largest sea cucumbers, which are highly exploited throughout the Indo-Pacific. At two coral reef sites at Lizard Island, northern Australia, we tracked the 2-hourly displacement of individuals from morning to nightfall. Movement of T. ananas was more reef-associated and tortuous than T. anax. Displacement rates averaged 80 cm h⁻¹ (±8 SE) for T. ananas and 73 cm h⁻¹ (±20) for T. anax. Body size accounted for half of the variation in displacement for T. ananas. Mobility peaked in the late afternoon or early evening for both species, and animals tended to reverse their direction of travel after midday. The data reflect a pattern of animals meandering out from their reef shelters onto sandy lagoon floors to forage, before returning to the reefs. This empirical evidence offers further support that these holothuroids contribute to the formation of “reef halos”. The exceptionally high movement rates and patterns found in this study should inform the design of spatial management measures.

Compositional similarity generally decreases with increasing geographic distance between sites (distance decay of similarity, DDS). Two non-exclusive mechanisms have been proposed to explain this pattern: increasing differences in environmental conditions and pure spatial effects of dispersal limitation. On regional and global scales, environmental selection is considered the major factor for microbial assemblages, whereas pure spatial effects are generally more profound for larger organisms with limited dispersal ability. We investigated the DDS relationships at a small spatial scale (decimeters - tens of meters) for three groups of benthic organisms differing in body size: diatoms and flagellates (DF), ciliates (CL), and harpacticoids (HA). All groups demonstrated definite DDS relationships. The pure spatial effects were strongest for the smallest-size protists (DF), relatively weaker for CL and negligible for HA. In contrast, environmental factors (i.e., the differences in sediment properties) were more important for the HA and CL assemblages than for DF assemblages. In addition, we revealed a considerable temporal component of DDS relationships. First, similarity decreased with the time interval between sampling events (“temporal DDS”). Second, the average spatial similarity itself increased with time. These effects were significant for DF and CL only but were weak or undetectable for HA. Thus, our results are opposite to those commonly observed at larger (regional or global) scales. We suppose that the DDS relationships obtained at different spatial scales, despite formal similarity, reflect different phenomena driven by different mechanisms. At the geographical scale, species distribution patterns are mainly driven by long-distance dispersal processes operated at the population level and dependent on their size-related traits, which, taken in common, offer the advantage of small-sized groups. The local-scale distribution is primarily determined by individual motility and within-habitat environmental heterogeneity. Small protists are relatively less motile, finely perceived and, therefore, have higher rates of spatial decay.

Anthropogenic disturbances affect the health of coral reefs worldwide and may also impact hawksbill (Eretmochelys imbricata) foraging areas, potentially decreasing sponge numbers, while increasing macroalgae. Few studies have been conducted to understand energy content of hawksbill prey. We investigated observed (Geodia neptuni and Kallymenia limminghii) and potential (Xestospongia muta and Halimeda opuntia) hawksbill prey abundances and their energy contents in the Sandy Bay West End Marine Reserve, and related prey distribution to hawksbill distribution within the reserve. We analysed prey abundances by conducting in-water habitat transects followed by point count analyses. In-water hawksbill observations were recorded to provide total times turtles foraged on prey. We then measured energy content of prey types using microbomb calorimetry. Habitat assessments indicated sponges were most abundant in West Bay and West End, whereas macroalgae were most abundant in West End. Foraging observations indicated juvenile hawksbills spent more time foraging on G. neptuni (x̅ = 236.5 s) than K. limminghii (x̅ = 98.0 s) and no time foraging on either X. muta or H. opuntia. Energy content was higher for G. neptuni (4.09 kJ g⁻¹) and K. limminghii (12.88 kJ g⁻¹) than X. muta (2.48 kJ g⁻¹) and H. opuntia (1.27 kJ g⁻¹). Hawksbills were frequently observed feeding in West Bay where sponges were abundant and were also observed foraging on K. limminghii throughout this area. Fewer hawksbills were observed in West End and Sandy Bay than in West Bay, and these areas had fewer sponges compared with West Bay. Hawksbills benefit from foraging on the abundant observed sponge and macroalgae within their home ranges, allowing them to conserve energy and increase potential net energy gains from high energy prey.