Marine Ecology-An Evolutionary Perspective最新文献

Biological diversity can be evaluated by the taxonomic and functional components. This study aimed to assess the relationship between taxonomic richness with the functional diversity components [functional richness (FRic), functional evenness (FEve) and functional divergence (FDiv)] and the functional trait dominance of polychaetes. In addition, we evaluated the environmental parameters that shape the functional structure in six tropical estuaries in north-eastern Brazil. Three estuaries have a continuous environmental gradient (typical tropical), and the other three estuaries have no defined environmental gradient (semiarid tropical). We identified significant differences in the dominance of feeding strategy and habitat between estuaries, demonstrating that the functional space of the communities is not equally occupied. Also, the substrate particle size composition was correlated with the functional structure. FRic showed a positive relationship with taxonomic richness, regardless of the type of estuary. As taxonomic richness increases, the probability of different combinations of functional categories added to a community also increases. FEve and FDiv seem to be independent of taxonomic richness. Therefore, it is important to simultaneously evaluate diversity's taxonomic and functional components, considering the complementarity of the information provided by these diversity measures.

The two-toned pygmy squid (Idiosepius pygmaeus, Steenstrup, 1881) is a small, tropical cephalopod that inhabits seagrass meadows and is known to attach to blades of seagrass using a specialised adhesive organ. A global decline in seagrass habitat due to anthropogenic disturbances may threaten the species that rely on seagrass meadows for shelter, foraging and other crucial activities. It is unclear if I. pygmaeus can utilise alternative habitats in the absence of seagrass. Here, we test the effect of habitat type, material and composition type, and the presence of conspecifics on the settlement preferences of I. pygmaeus. Individuals each underwent three separate experiments: (1) testing the preference between their known habitat, Zostera muelleri subsp. Capricorni and potential substitute, Sargassum, (2) testing the preference to attach to a natural or artificial structure of similar shape and size, and (3) testing the preference of identical habitats, one with a conspecific adhered to and one without. We found that I. pygmaeus did not have a strong preference for either Zostera or Sargassum. However, a strong preference was found for attachment to the natural structure over the artificial one. There was also strong evidence for the use of conspecific cues in habitat choice, with 75% of individuals selecting the habitat that contained a conspecific. As habitat loss is the leading cause of species extinction, the knowledge of habitat preferences for I. pygmaeus is vital in order to assess their risk of population decline. The findings of this study suggest that I. pygmaeus could utilise an alternative habitat in the presence of seagrass meadow reduction, which is under threat from human activity.

Abundant clam populations provide ecosystem services and commercial and recreational shellfish harvests worldwide. Two non-native clams (Manila clams, Ruditapes philippinarum; eastern soft-shell clams, Mya arenaria) commonly populate mid-intertidal zones of coarse-sediment beaches in Washington State, USA. To better understand factors influencing their abundance, we used passive mid-intertidal spat collectors to determine the density and distribution of clam recruits (150–500 μm shell length) at eight beaches spanning over 500 km and over two reproductive seasons (2016 and 2017). Cumulative seasonal recruitment (clams <500 μm) in 2016 and 2017 at +1.0 m MLLW ranged from 800 to 125,000 m⁻² for Ruditapes philippinarum and 50–85,000 m⁻² for M. arenaria, and did not differ by substrate type at small scales (gravel vs. crushed shell). At larger scales, different interannual recruitment patterns across sites did not dramatically shift the ranked order of highest and lowest recruitment sites. Cumulative recruitment tended to be lower at warmer sites, while timing of peak recruitment was not consistently related to temperature. Sites also differed in the relative recruitment of the two clam species, but most beaches had greater densities of R. philippinarum than M. arenaria at both recruitment and juvenile stages. Although recruitment densities differed by two orders of magnitude across sites, post-settlement factors eliminated initial spatial variation within a year, dampening recruitment variability among these beaches that all contribute to commercial and recreational clam production.

Latitudinal biodiversity gradients vary across taxonomic groups and spatial scales, and various environmental factors have been associated with those patterns. However, it remains unknown whether taxonomic groups with strong ecological associations have similar or different latitudinal patterns. Macroalgae are foundation assemblages on rocky intertidal shores and are often inhabited by invertebrates, predominantly polychaetes. This study analysed latitudinal patterns of macroalgae and their associated polychaetes at different spatial scales and determined how environmental factors influenced those patterns. Macroalgae and polychaetes were collected from transects within 38 rocky intertidal shores of Western Australia at 14 latitudes between 18° S and 34° S. Latitudinal gradients in species richness, diversity (Simpson's diversity index) and abundance were evaluated at transect, site and latitudinal scales. Relationships between environmental factors and rocky intertidal assemblages were analysed using piecewise structural equation modelling based on direct, indirect and complex models. Macroalgae showed increases in species richness, diversity and abundance at transect and site scales towards high latitudes, but species richness and diversity patterns were unclear at the latitudinal scale where transect and site data were pooled. In contrast, polychaete diversity decreased towards high latitudes, although this pattern was unclear at the transect scale. Polychaete richness and abundance tended to follow parabolic patterns that peaked at 27° S. Relationships between environmental factors and rocky intertidal assemblages were best described by a complex model, with significant relationships more often at transect and site scales. Sea surface temperatures showed the strongest relationship with macroalgal and polychaete distributions.

As coral reefs continue to decline due to anthropogenic stressors, community characterizations will reveal both historical selection processes and adaptive potential to environmental change. To address the potential role of color in the distribution and resilience of massive Porites corals, we surveyed the distributions of two dominant color morphs (brown and purple), and a unique intermediate state, across a depth gradient in Guam, Micronesia. We found that brown colonies dominated populations across all depths, and larger colonies had higher rates of partial tissue mortality and active disease lesions. Despite the dominance of brown colonies, both brown and purple color morphs showed a high similarity in susceptibility, as indicated by the colony sizes, the severity of partial tissue mortality, and the prevalence of active disease lesions. This is a non-intuitive result given the presence of phenotypic plasticity between color morphs, evident by an intermediate, transitionary stage between brown and purple colonies that suggests a functional divergence between one color over the other. The study also revealed the dominance of small colonies at depth, which provides some insight into the ecological impacts that may have shaped Guam's current massive Porites population size structure over the past several decades. With this, we provide foundational insight into the adaptive strategies and historical pressures that have shaped the modern massive Porites population.

Research on intertidal mussel assemblages and associated communities has revealed that complexity and structure are influenced by environmental heterogeneity and local-scale factors affecting recruitment. Research in situ in eastern and western Pacific intertidal ecosystems has suggested drivers of species diversity and community structure encompassing large geographic scales, however, there are major gaps in geographic coverage. Our aim is to fill some of these gaps by analyzing macrofaunal functional group diversity and effects of environmental factors on intertidal mussel communities from three distinct marine ecoregions in the southern and northern hemispheres. We identified the effects of algal cover and environmental heterogeneity on species richness and evenness, and we modeled factors effecting mussel layer complexity from assemblages in three marine ecoregions. We analyzed macrofaunal species diversity within one of the austral ecoregions based on the width of the coastal shelf. Species richness was highest in samples from the northern hemisphere while evenness was highest in samples from the southern hemisphere. Similarity in functional group structure for all communities sampled was ≤55% (Bray–Curtis dissimilarity) and ≤35% (Chao–Jaccard dissimilarity). Wave exposure had a significant effect on shell length and complexity of mussel matrices on rocky bench platforms. The presence of algal cover had a strong effect on species richness in mussel matrices regardless of complexity, while algal canopies had no effect on species evenness. Overall, this study provides significant new insight on the community complexity of mussel beds in parts of the world which have been poorly studied in this regard.

The foraminifera and tintinnids are essential indicators of the health status of marine and estuarine ecosystems, both past and present, and can be used for monitoring purposes in the future. Tintinnids are known to group among ciliates possessing hard loricate to be considered by hydrogeologists as one of the bio-indicator species, exhibiting a strong positive correlation with phytoplankton. Pulicat Lake is a marginal marine environment present near the south coast of India. Intertidal sediment samples were collected from September 2013 to August 2014 and were subjected to isolate the foraminiferans and tintinnids by adopting standard methods. In all, twenty-one genera and 24 species of foraminifera have been identified from the stream, where Quinquelina seminulum was found to be abundant. Contrary to this, a minimum number of species was present in the freshwater inflow zone, mainly Amomalinula glabrata, Haplophragmoides kirki, Natlandia secasensi and Valvulineria candeiana. Tintinnopsis are recorded in the sampling sites, belonging to 5 families and 6 genera, and 12 species have been identified, and among these Favella campanula species was found to be abundant in the study area. From our results, the recorded species in terms of numerical abundance of foraminiferans appeared predominant over the tintinnids. The dominant role of foraminiferans may be a significant contribution to the carbon cycle of marine/estuarine ecosystems proved elsewhere in turn responsible for the substantial uptake of phytodetritus deposition. Based on these findings, our preliminary study may be useful to explore the carbon sequestration process in the Pulicat Lake ecosystem.

Beach seine fishery provides a means of livelihood to many households in Africa and it is widely practiced in the coastal communities of Ghana due to the relatively cheaper operational cost. However, the small mesh sizes of beach seine nets and fishing activities that involve dragging a net through the nearshore seabed tend to destroy fish breeding grounds and capture juvenile fish and non-target benthic macroinvertebrates, which get discarded. This study investigated the impact that before and after closed season for beach seine fishing had on macroinvertebrates species diversity indices at two Ghanaian beaches with different fishing pressures. The study was carried out at OLA and Sisimbo Beaches located in the Central Region of Ghana, taking advantage of the statutory 1-month national fishing closed season in July 2022. Six (6) replicate sediment samples were taken at each beach after landing by beach seine fishers every month for 6 months, from April to June, and August to October, representing before and after closed season, respectively. Benthic macroinvertebrates were retrieved from the samples using appropriate protocols and subjected to indirect (Shannon, Simpson, Rényi) and direct (species abundance models, species accumulation models, multivariate statistics) measures of species diversity analyses. The indirect species diversity indices increased monotonically the following 2 months after closed season but reduced in the third month after closed season at both beaches. Conversely, the direct measures of diversity indices revealed that closed season for beach seine fishing improved species numbers and richness at both study beaches. This is the first report on the impact of a closed season on macroinvertebrates in any African country.

The dispersal mode of estuarine invertebrates has a strong effect on genetic variability and phenotypic expression, potentially maintaining gene flow among widely separated populations or limiting connectivity among close ones. Understanding the dispersal strategies effects can support adequate strategies for environment management and understand the evolutionary history of the studied species. A comparative study on the effect of larval dispersal strategies (export vs retention) along the overall geographic distribution ranges of adult populations of two co-distributed fiddler crab species was performed. Geometric morphometric techniques were used to evaluate morphological differentiation in the shape of the carapace and major cheliped propodus in 10 populations of Minuca mordax and five populations of Leptuca leptodactyla. Potential genetic differentiation was assessed using DNA sequence data from up to 170 fiddler crab specimens, corresponding to the mitochondrial gene cytochrome c oxidase subunit 1 (COX1). Patterns of genetic and morphological characteristics diverged among populations of both species. In terms of morphology, populations of both species showed intraspecific variation in the shape of the carapace and, to a lesser extent, in the major cheliped propodus. This observed intraspecific variation followed a clear geographic pattern of morphometric differentiation, in which the geographic origin is associated with a phenotypic response to the environmental diversity along the extended Brazilian coast. In contrast, there are shared haplotypes in populations separated by more than 4000 km, but with significant Φ_ST values among most populations of L. leptodactyla and M. mordax, suggesting a moderate to high level of gene flow. Therefore, it can be concluded that the split of the Central South Equatorial Current has not acted as an efficient long-term barrier to the dispersal of larvae in both species. In M. mordax, a slight limitation of genetic exchange can be observed between the southernmost populations and the remaining ones. This first evidence of genetic structuring within this widely distributed species is consistent with its documented strategy to retain larvae in the estuarine environments. However, occasional transport of larvae to more open coastal waters seems to maintain stepwise gene flow between neighboring populations. Overall, our results still provide evidence of more pronounced genetic homogeneity in a species with a larval export strategy (L. leptodactyla) compared to a species with a larval retention strategy (M. mordax). This suggests that larval dispersal strategies, coupled with the microhabitat in which the respective species occur, have a noticeable effect on the degree of gene flow. Most likely, these biological aspects are further influenced by the estuarine and coastline geomorphology.

Ubiquitous, industrial use of bottom-towed fishing gear since the 1800s has altered marine communities and ecosystem services. Outside of legal protection, only areas inaccessible to trawlers are offered any protection. Shipwrecks present hazards to fishing gear and are rarely subject to trawling pressure. As many have been in situ for >100 years, they offer a baseline of ecological potential when trawling pressure is reduced or removed. Five shipwrecks were surveyed off the Berwickshire coast, some within the Static Gear Reserve and others outside. Video transects were collected of shipwrecks, the surrounding 50 m radius and control locations >150 m from the wreck site. Species identified were assigned a category based on their vulnerability to trawling. The effect of distance from a shipwreck on ecological communities within sites Open and Closed to trawling was investigated. The ecological importance of shipwrecks increased relative to trawling pressure. In Open sites, abundance was 340% greater on Wreck locations than Control. Conversely, within Closed sites, abundance was 149% greater in Control locations than Wreck. In Open sites, shipwreck communities are more similar to those in Closed sites, than to the habitat surrounding the shipwreck. Vulnerable species, mostly large, sessile filter feeders, are almost entirely absent from Open sites, but account for ~28% of the total abundance on shipwrecks in Closed sites. This study offers a quantifiable method to evaluate the ecological contribution of shipwrecks in disturbed areas and suggests their role may warrant further research, and consideration in conservation policy, such as inclusion in 30 × 30 objectives. Our findings also demonstrate the possible ecological gains of expanding or including static gear reserves across Marine Protected Areas.