Shallow-water Ecosystems Research Articles

Impact of invasive apple snails on shallow water ecosystems under different nutrient conditions: results from a mesocosm study

Impact of invasive apple snails on shallow water ecosystems under different nutrient conditions: results from a mesocosm study

Coastal and Marine Ecosystems of the Arafura and Timor Seas – Characterization, Key Features and Ecological Significance

The tropical Arafura and Timor Seas (ATS) region lies on the edge of the Coral Triangle, located at the intersection of two major Large Marine Ecosystems, the Northern Australian Shelf and the Indonesian Sea. Under the influence of the Indonesian Through Flow current and Pacific-Indian Ocean exchange, the ATS also lies at a major ‘cross-road’ of global ocean circulation and climate regulation. The ‘semi-enclosed’ ATS is characterized by diverse seascapes, pronounced ecological connectivity (marine biodiversity, shared fisheries, land-sea interactions), extensive coastal wetlands and shallow-water ecosystems, and globally-significant marine biodiversity (particularly corals reefs, mangroves, seagrasses, and populations of marine megafauna). Complex oceanography, bathymetry and large-scale, tidal and monsoon-driven circulation, and localized, seasonal upwellings are major features across the region, driving patterns of ocean productivity, reef biodiversity and sustaining rich pelagic ecosystems. With some of the most extensive, productive and near-pristine tropical coastal ecosystems in the world, the waters of the ATS are a global marine biodiversity ‘hotspot’ and play a crucial role in maintaining regional/global tropical marine biodiversity. Including providing major migration corridors, critical habitats and a regional/global refuge for some of the world’s most threatened marine megafauna and wildlife populations (particularly sea turtles, sharks/rays, sawfish/river sharks, whales, dolphins and dugongs). Coastal habitats in the ATS also provide a range of ecosystem services of fundamental importance to human well-being, including climate change; with climate-resilient coral reefs and some of the largest and intact, tropical wetlands (mangroves, saltmarshes, seagrasses) in the world, the ATS region is a recognized global blue carbon hotspot. The characterization and assessment of key ecosystems and processes in the ATS in this study provide the basis for protecting these resources through the Arafura and Timor Seas Ecosystem Action Program.

Rainstorm and strong wind weathers largely increase greenhouse gases flux in shallow ponds

Shallow-water ponds represent the hotspots of greenhouse gas (GHG) emissions. Most current studies focus on the temporal dynamics for GHGs in water, with little consideration given to the effects of weather changes. In this study, we measured and compared the concentrations and fluxes of CO2, CH4, and N2O from a pond in Northeast China under different meteorological conditions. Results showed that the rates of CO2, CH4, and N2O emissions from pond into the atmosphere during strong winds were 85.85 ± 7.55 mmol m−2 d−1, 22.05 ± 6.80 mmol m−2 d−1, and 10.87 ± 0.72 μmol m−2 d−1, respectively, significantly higher than those measured during non-rain weather. Among which, over 88 % of CH4 emissions were contributed by ebullition. Meanwhile, the CO2 and N2O flux were also significantly higher during heavy rainfall, reaching 100.05 ± 19.76 mmol m−2 d−1 and 5.90 ± 1.03 μmol m−2 d−1, respectively. Strong winds and precipitation induced sediment disturbances, high gas transport coefficients, reduced photosynthesis and oxygen greatly promoted the GHGs escape evasion. Wind speed, air pressure, solar radiation, and dissolved oxygen in water were important influencing factors. Our results emphasize the importance of capturing short-term weather disturbance events, especially rainstorm and strong winds, to accurately assess the annual GHG budget from these shallow water ecosystems.

Projections of changes in the global distribution of shallow water ecosystems through 2100 due to climate change

The global area and distribution of shallow water ecosystems (SWEs), and their projected responses to climate change, are fundamental for evaluating future changes in their ecosystem functions, including biodiversity and climate change mitigation and adaptation. Although previous studies have focused on a few SWEs, we modelled the global distribution of all major SWEs (seagrass meadows, macroalgal beds, tidal marshes, mangroves, and coral habitats) from current conditions (1986–2005) to 2100 under the representative concentration pathway (RCP) 2.6 and 8.5 emission scenarios. Our projections show that global coral habitat shrank by as much as 75% by 2100 with warmer ocean temperatures, but macroalgal beds, tidal marshes, and mangroves remained about the same because photosynthetic active radiation (PAR) depth did not vary greatly (macroalgal beds) and the shrinkage caused by sea-level rise was offset by other areas of expansion (tidal marshes and mangroves). Seagrass meadows were projected to increase by up to 11% by 2100 because of the increased PAR depth. If the landward shift of tidal marshes and mangroves relative to sea-level rise was restricted by assuming coastal development and land use, the SWEs shrank by 91.9% (tidal marshes) and 74.3% (mangroves) by 2100. Countermeasures may be necessary for coastal defense in the future; these include considering the best mix of SWEs and coastal hard infrastructure because the significant shrinkage in coral habitat could not decrease wave energy. However, if appropriate coastal management is achieved, the other four SWEs, which have relatively high CO2 absorption rates, can help mitigate the climate change influences.

PCO2 decrement through alkalinity enhancement and biological production in a shallow-water ecosystem constructed using steelmaking slag

Ocean-based carbon dioxide removal has gained immense attention as a countermeasure against climate change. The enhancement of ocean alkalinity and the creation of new blue carbon ecosystems are considered effective approaches for this. To evaluate the function of steelmaking slag from the viewpoints of CO2 reduction and creation of new blue carbon ecosystems, we conducted a comparative experiment using two mesocosms that replicated tidal-flats and shallow-water ecosystems. Initially, approximately 20 seagrasses (Zostera marina) were transplanted into the shallow-water area in the mesocosm tanks. The use of steelmaking slag is expected to increase the pH by releasing calcium and mitigate turbidity by solidifying dredged soil. In the experimental tank, where dredged soil and steelmaking slag were utilized as bed materials, the pH remained higher throughout the experimental period compared with the control tank, which utilized only dredged soil. As a result, pCO2 remained consistently lower in the experimental tank due to mainly its alkaline effect (March 2019: −10 ± 6 μatm, September 2019: −130 ± 47 μatm). The light environment in the control tank deteriorated due to high turbidity, whereas the turbidity in the experimental tank remained low throughout the year. The number of seagrass shoots in the experimental tank was consistently approximately 20, which was higher than that in the control tank. Additionally, more seaweed and benthic algae were observed in the experimental tank, indicating that it was more conducive to the growth of primary producers. In conclusion, tidal-flat and shallow-water ecosystems constructed using dredged soil and steelmaking slag are expected to enhance CO2 uptake and provide a habitat for primary producers that is superior to those constructed using dredged soil only.

Pemetaan Sebaran Habitat Dasar Perairan Laut Dangkal Menggunakan Citra Sentinel-2A di Teluk Gilimanuk

West Bali National Park is a conservation area with such a high biodiversity. That includes mangrove forest, coastal, and shallow water ecosystem. As a conservation area, a distribution map of the shallow water habitat is necessary for decision making in the conservation’s benthic habitat developing program. One of the mapping method is remote sensing and requires Sentinel-2A Level 1C satelitte image. Sentinel-2A Level 1C is used due to its high resolution which is 10x10 meters for a single pixel. The aim for this research is for mapping the distribution of the shallow water habitat in Gilimanuk Bay while also assesses the accuracy of Sentinel-2A image. This research uses the Quantum GIS and SAGA GIS software to analyze the Sentinel-2A image. The image is transformed using Depth Invariant Index to reduce the scattering effect on the reflectance. After the image is being transformed by the Depth Invariant Index, it is classified using maximum likelihood method. The classification showed, the area of each classes are 56.59 hectares of corals, 18.01 hectares of seagrass, 128.97 hectares of waters, 45.76 hectares of mud sediment, 78.95 hectares of macro algae, and 26.67 hectares of sands. Overall accuracy assessment for this research calculated using confusion matrix and the result is 65.1% and considered good enough due to Coral Ecosystem Remote Sensing Data Analysis Guide by National Institute of Aeronautics and Space (LAPAN), in which the tolerance of the accuracy is 60%. Accuracy levels are influenced by number of classes, image resolution, class resemblance, turbidity, and seafloor material.

Three decades of variability and warming of nearshore waters around Tasmania

The ocean region around Tasmania forms an interface between major ocean basins and represents a significant global ocean hotspot due to a rate of warming higher than the global average. Nearshore Tasmanian waters are of central importance for shallow-water ecosystems and a range of human activities, including recreation, aquaculture and fisheries which have become increasingly impacted by warming in recent decades. However, the fine-scale spatial and temporal variability of sea surface temperature (SST) in these waters is not well understood, limiting opportunities for effective local-scale mitigation and adaptation measures in the face of ongoing warming. We use a high-resolution (0.02 °x 0.02°, 1992–2020) satellite SST received at local stations (validated against in situ temperature) to explore variability over seasonal, interannual, decadal and multi-decadal timescales at spatial scales from the nearshore up to the entire study domain. The SST is used as a proxy for seasonal circulation by removal of the broad-scale radiative forcing (estimated by a region-wide latitudinal gradient of SST). The main circulation drivers of nearshore SST are the East Australian Current Extension (EACx) and Zeehan Current (ZC) acting on the east and west coasts with respective peaks in summer and winter. New results include the seasonality of three summer upwelling systems, the first direct evidence of EACx inflow into eastern Bass Strait, a time series of the endpoint of the ZC/EACx intersection, and a full year description of the ZC, from warm winter inflow transitioning into a summer cooler than ambient intrusion. We find that local SST variations are controlled by coastal geometry with intensified atmospheric forcing in enclosed waters. We have identified two modes of low frequency SST variability (including 1, 2 and 10-year periods) associated with the EACx (63% of the variance) and the ZC (12%). The EACx mode induces a rapid adjustment of the entire ocean region around Tasmania. Multi-decadal warming trends occur in all regions, modulated by coastal boundary flows, changes in upwelling mechanisms and local topography. Trends in the eastern shelf arise from intrusions of EACx waters, with local processes driving trends on the western shelf. Both east and west nearshore SST trends are around + 0.4°C decade−1 with the highest value of + 0.55°C decade−1 on the central west coast, possibly associated with outflow from Macquarie Harbour.

The use of radiocarbon to evaluate the trophic role of geothermal bacteria in shallow hydrothermal water ecosystem

Stable isotopes such as δ13C and δ15N are routinely used in trophic ecology as isotope values are derived from diet and recorded subsequent fractionation in consumer tissue. However, this approach necessitates to estimate a priori the fractionation between food source and consumer leading to potential uncertainties. In this context, the development of additional biomarkers enables to have better resolution on feeding habits. Dissolved Inorganic Carbon (DIC) from volcanic activity and bacteria using this DIC presents a strongly depleted natural radiocarbon abundances (Δ14C). Through its activity, the geothermal plant of Bouillante in Guadeloupe (French West Indies) releases sulfur bacteria in shallow environment of the Bay. A previous study reveals ingestion of those bacteria by opportunist species (sea urchin and fish species). In the present study, ten species with different diet and feeding mode were sampled close to the release channel of the geothermal plant and in a control station in order to simultaneously determine their stable isotopes (δ13C and δ15N) and radiocarbon compositions. Compared to models using Δ14C data, models using δ13C and δ15N data underestimate the role of bacteria in diet of urchin and fish species whereas this role is overestimated for all other species. Compared to previous models, radiocarbon would give more realistic and reliable results than the classical use of stable isotope. This study confirms the utility of radiocarbon in food web ecology, particularly at the ecosystems having food sources with contrasting Δ14C values.

Predicting Coral Reef Carbonate Chemistry Through Statistical Modeling: Constraining Nearshore Residence Time Around Guam

To accurately predict the impacts of ocean acidification on shallow-water ecosystems, we must account for the biogeochemical impact of local benthic communities, as well as the connectivity between offshore and onshore water masses. Estimation of residence time can help quantify this connectivity and determine the degree to which the benthos can influence the chemistry of the overlying water column. We present estimates of nearshore residence time for Guam and utilize these estimates to model the effects of benthic ecosystem metabolism on the coral reef carbonate system. Control volume and particle tracking approaches were used to estimate nearshore residence time. These estimates were paired with observed patterns in the reef carbonate system around Guam using water samples collected by NOAA’s National Coral Reef Monitoring Program. Model performance results suggest that when considering the effects of benthic metabolism on the carbonate system, it is paramount to represent the contact time of the water volume with the benthos. Even coarse estimates of residence time significantly increase model skill. We observed the highest predictive skill in models including control volume derived estimates of residence time, but only when those estimates were included as an interaction with benthic composition. This work shows that not only is residence time critically important to better predict biogeochemical variability in coral reef environments, but that even coarse hydrodynamic models can provide useful residence time estimates at management relevant, whole-ecosystem scales.

Dissolved Nitrous Oxide in Shallow-Water Ecosystems under Saline-Alkali Environment

The problem of global warming is becoming more and more serious. N2O is a potent greenhouse gas. Most current studies on dissolved N2O concentration have focused on inland freshwater and seawater while paying less attention to coastal agricultural catchment areas. The coastal agricultural catchment area is the link between the farmland ecosystem and the aquatic ecosystem, which is shallow in water depth. Moreover, due to the high salt content and obvious periodic change, it is highly sensitive to environmental changes and human activities and has strong potential for N2O emission. Therefore, it is of great significance to understand the characteristics of the changes in the dissolved N2O concentration in the shallow-water ecosystem under the saline-alkali environment of the coastal reclamation area and to identify the main controlling factors. The soil of Yudong reclamation area in Rudong County, Jiangsu Province was collected to carry out the submerged cultivation experiment. In order to simulate the saline-alkali situation of the coastal reclamation area, four salt gradients (S1–S4), four alkali gradients (A1–A4), and three levels of exogenous nitrogen concentration (N1–N3). In addition, the experiment set a control treatment (CK) without salt and alkali addition. After 2 weeks of cultivation in a shallow water layer of about 5 cm, the dissolved N2O concentration and its influencing factors were measured and analyzed by collecting the overlying water sample and sediment after 24 h of fertilization. The results showed that changes in the saline-alkali environment in shallow-water ecosystems significantly affected the changes in dissolved N2O concentration. The saline-alkali indicators (EC and pH of the overlying water and sediment), DO of the overlying water, and the microbial genes nirS, nirK, and nosZ were the key influencing factors of N2O production in shallow-water systems. The correlation between nirS gene abundance and the dissolved N2O concentration was the highest. The BP neural network model can be used to simulate and predict the dissolved N2O concentration in overlying water under saline-alkali environment. Based on the experimental results, this study can provide a scientific basis for understanding the nitrogen cycling process in shallow-water ecosystems in the coastal reclamation area, improving the absorption of non-point-source nitrogen and reducing N2O emissions in shallow-water wetlands.

Effects of Algae on the Formation of Black Blooms and Bacterial Community Structure Changes in Sediments and Black Floats

Black bloom is a phenomenon of serious deterioration in shallow-water ecosystems worldwide. This study investigated the effects of algae on the formation of black blooms and the changes of the bacterial community using nearly in-situ cores for a 40-day indoor simulation. We designed experiments with different combinations of water (W), sediments-water (SW), and sediments-water-algae (SWA), and made a comparative analysis of bacterial communities in sediments and black floats. The results demonstrated that the severity of black blooms was considerably affected by the presence of cyanobacteria. The concentration of total nitrates (TN) and NH4+-N in the SWA group increased to 25.1 and 22.47 mg/L (4.05 and 5.5 times of their initial concentrations), respectively. The abundance of microorganisms in the sediments was significantly higher than that of the black floats. The dominant species in both sediments were Proteobacteria and Chloroflexi, whose total proportion exceeded 50%. The addition of algae did not change the dominant community of the sediments. In black floats, the dominant species of the SW group were Proteobacteria (39%) and Actinobacteria (16%), and these of the SWA group were Proteobacteria (38%) and Cyanobacteria (35%). The dominant species in black floats changed significantly. Cyanobacteria increased remarkably in black floats in the group of algae additions. The possible reason may be that the Actinobacteria were suppressed by Cyanobacteria. Therefore, the addition of algae has a significant promoting effect on black blooms and significantly affects the microbial community structure of black floats.

THE ASSOCIATION OF BENTHIC MACROBIOTA OF THE LATE EDIACARAN OF PODILLIA IN THE DEPOSITS OF THE MOHYLIV-PODILSKYI GROUP IN THE QUARRY NEAR THE DNIESTER HPP

The maximum level of Ediacaran-type biota diversity in the Volyn-Podilskyi sedimentation basin existed in the time interval that corresponds to the Lomoziv and Yampil Members of the Mohyliv Formation. Studies of the isotopic age showed that this period ended 557 million years ago. Environmental conditions that prevented the existence of classical Ediacaran biota prevailed during the accumulation of the Lyadova Member. A less numerous biotic association of the transitional type with individual representatives of the Ediacara-type association is observed in the deposits of the Bernashivka Member. Paleoecological conditions in the sedimentation basin were reconstructed on the basis of the study of the section in the quarry near the Dniester HPP. More than a thousand specimens of fossils of soft-bodied organisms and tracefossils were collected there. More than three dozen species were discovered in Podilla for the first time. The study of a significant number of new species continues. It was established that the biotic association of the Mohyliv Formation was dominated by problematic frondomorphic and spherical organisms, which sometimes reached significant sizes.The existence of probable ancestors of several groups of biota of the Phanerozoic type:Cnidaria, Porifera, Lophotrochozoa, Mollusca and Metaphita were found in the Late Ediacaran shallow water ecosystem. Thefossil remains of the earliest probable members of the phylum Chordata of the subphylum Tunicata are collected here. These arethe most likely ancestors of vertebrates according to data from several research groups. It was established that some Ediacaran organisms used life strategies typical for representatives of later biota: combinations of different types of reproduction, activeresponse to external environmental factors, etc. New methods of fossil research were proposed and important results were obtained in the process of their use. It was established that quite sharp changes in the taxonomic composition of biotic associations in the section of sediments are caused by facies conditions and evolutionary processes. This makes it possible to use the fossilized remains of the Ediacaran biota for the needs of biostratigraphy and correlation with the same age deposits in other regions.

Harnessing solar power: photoautotrophy supplements the diet of a low-light dwelling sponge

The ability of organisms to combine autotrophy and heterotrophy gives rise to one of the most successful nutritional strategies on Earth: mixotrophy. Sponges are integral members of shallow-water ecosystems and many host photosynthetic symbionts, but studies on mixotrophic sponges have focused primarily on species residing in high-light environments. Here, we quantify the contribution of photoautotrophy to the respiratory demand and total carbon diet of the sponge Chondrilla caribensis, which hosts symbiotic cyanobacteria and lives in low-light environments. Although the sponge is net heterotrophic at 20 m water depth, photosynthetically fixed carbon potentially provides up to 52% of the holobiont’s respiratory demand. When considering the total mixotrophic diet, photoautotrophy contributed an estimated 7% to total daily carbon uptake. Visualization of inorganic 13C- and 15N-incorporation using nanoscale secondary ion mass spectrometry (NanoSIMS) at the single-cell level confirmed that a portion of nutrients assimilated by the prokaryotic community was translocated to host cells. Photoautotrophy can thus provide an important supplemental source of carbon for sponges, even in low-light habitats. This trophic plasticity may represent a widespread strategy for net heterotrophic sponges hosting photosymbionts, enabling the host to buffer against periods of nutritional stress.

Are fatty acids in fish the evidence of trophic links? A case study from the southern Baltic Vistula Lagoon

Most knowledge on the feeding ecology of fish has been based on the analyses of food remains from the alimentary tracks. This traditional method, however, only provides information about recently consumed food, and is burdened with a risk of incorrect assessment of the role of individual diet components due to the different rates of digestion. A method free from such limitations is the analysis of fatty acids. The objective of our study was to recognise the potential of fatty acid signatures in providing information on the diet and feeding habits of six fish species from the shallow brackish Vistula Lagoon, southern Baltic Sea (Anguilla anguilla, Abramis brama, Rutilus rutilus, Pelecus cultratus, Perca fluviatilis, Sander lucioperca). Multivariate statistical analyses of fatty acid signatures permitted relevant grouping of the fish according to species and their diet, as well as evidenced substantial ontogenetic changes in perch, roach, and bream. They might be caused by dietary changes but can also result from internal regulatory processes. The obtained results confirmed that fatty acids provide useful, time-integrated dietary information, contributing to expanding knowledge regarding the feeding ecology of fish in shallow coastal water ecosystems. They also pointed to the necessity of assessment of the invertebrates and fish's ability to perform endogenous synthesis of polyunsaturated fatty acids, particularly in research on benthic communities. To our best knowledge, this is the first attempt to investigate the feeding habits of fish and food-web relationships in the coastal waters of the Baltic Sea using fatty acids.

Evaluation of Macrophyte Community Dynamics (2015–2020) in Southern Lake Garda (Italy) from Sentinel-2 Data

Macrophytes are of fundamental importance to the functioning of lake ecosystems. They provide structure, habitat, and a food source and are a required component in monitoring programs of lake ecological quality. The key aim of this study is to document the variation in spatial extent and density of macrophytes seasonally between 2015 and 2020 of the Sirmione Peninsula (Lake Garda, Italy), using Sentinel-2 imagery. In addition to this, our results were compared to previous data from imaging spectrometry; individual parameters affecting macrophyte communities were tested, and the possible effect of the COVID-19 lockdown on macrophyte colonization was evaluated. Satellite images allowed the mapping of the spatiotemporal dynamics of submerged rooted macrophytes in order to support monitoring of the shallow water ecosystem under study. Substantial changes were found in both spatial extent and density over the period from 2015 to 2020, particularly in 2019 when there was almost a complete absence of dense macrophytes. Variables found to influence the amount of macrophytes included transparency, chlorophyll–a, water level, winter wave height, and grazing by herbivores. A separate analysis focusing on areas associated with boat transit found a recovery in macrophyte coverage during the period of COVID-19 lockdown. The outcome of the study highlights a decline in the density of the macrophytes and a shift towards deeper areas compared to the situation in 1997. The area examined is part of an internationally important site containing the highest abundance and diversity of overwintering water birds in Italy. Exploiting satellite data at high frequency provided an insight to understand the dynamic changes and interactions with herbivorous birds, environmental factors, and anthropogenic pressures, revealing a delicately balanced and threatened ecosystem.

Drone-Based Characterization of Seagrass Habitats in the Tropical Waters of Zanzibar

Unmanned automatic systems (UAS) are increasingly being applied as an alternative to more costly time-consuming traditional methods for mapping and monitoring marine shallow-water ecosystems. Here, we demonstrate the utility of combining aerial drones with in situ imagery to characterize the habitat conditions of nine shallow-water seagrass-dominated areas on Unguja Island, Zanzibar. We applied object-based image analysis and a maximum likelihood algorithm on the drone images to derive habitat cover maps and important seagrass habitat parameters: the habitat composition; the seagrass species; the horizontal- and depth-percent covers, and the seascape fragmentation. We mapped nine sites covering 724 ha, categorized into seagrasses (55%), bare sediment (31%), corals (9%), and macroalgae (5%). An average of six seagrass species were found, and 20% of the nine sites were categorized as “dense cover” (40–70%). We achieved high map accuracy for the habitat types (87%), seagrass (80%), and seagrass species (76%). In all nine sites, we observed clear decreases in the seagrass covers with depths ranging from 30% at 1–2 m, to 1.6% at a 4–5 m depth. The depth dependency varied significantly among the seagrass species. Areas associated with low seagrass cover also had a more fragmented distribution pattern, with scattered seagrass populations. The seagrass cover was correlated negatively (r2 = 0.9, p < 0.01) with sea urchins. A multivariate analysis of the similarity (ANOSIM) of the biotic features, derived from the drone and in situ data, suggested that the nine sites could be organized into three significantly different coastal habitat types. This study demonstrates the high robustness of drones for characterizing complex seagrass habitat conditions in tropical waters. We recommend adopting drones, combined with in situ photos, for establishing a suite of important data relevant for marine ecosystem monitoring in the Western Indian Ocean (WIO).

Disentangling the Taxonomic Status of Caprella penantis sensu stricto (Amphipoda: Caprellidae) Using an Integrative Approach.

Despite its importance in intertidal and shallow-water marine ecosystems, Caprella penantis continues to be one of the most taxonomically challenging amphipods in the world. A recent molecular study focusing on C. penantis sensu stricto pointed out the existence of three highly divergent lineages, indicating the possible existence of a process of ongoing speciation and, thus, casting doubt on the taxonomic status of this species. In the present study, we used an integrative approach to continue to shed light on the taxonomy and distribution of this caprellid. To this end, we combined morphological and genetic data (COI and 18S) and included, for the first time, populations from its type locality. Our analyses provide strong evidence of the existence of potentially three distinct species, genetically and geographically restricted, within C. penantis sensu stricto, with the distribution of the true C. penantis sensu stricto restricted to the UK (type locality), the northern coast of the Iberian Peninsula, and the Azores. Results show the co-occurrence of two of these species in a locality of northern Portugal and indicate the existence of distinct evolutionary and diversification patterns along the eastern Atlantic region. Overall, our study highlights the use of an integrative approach to properly assess species boundaries and unravel hidden biodiversity in amphipods.

Open-Source Analysis of Submerged Aquatic Vegetation Cover in Complex Waters Using High-Resolution Satellite Remote Sensing: An Adaptable Framework

Despite being recognized as a key component of shallow-water ecosystems, submerged aquatic vegetation (SAV) remains difficult to monitor over large spatial scales. Because of SAV’s structuring capabilities, high-resolution monitoring of submerged landscapes could generate highly valuable ecological data. Until now, high-resolution remote sensing of SAV has been largely limited to applications within costly image analysis software. In this paper, we propose an example of an adaptable open-sourced object-based image analysis (OBIA) workflow to generate SAV cover maps in complex aquatic environments. Using the R software, QGIS and Orfeo Toolbox, we apply radiometric calibration, atmospheric correction, a de-striping correction, and a hierarchical iterative OBIA random forest classification to generate SAV cover maps based on raw DigitalGlobe multispectral imagery. The workflow is applied to images taken over two spatially complex fluvial lakes in Quebec, Canada, using Quickbird-02 and Worldview-03 satellites. Classification performance based on training sets reveals conservative SAV cover estimates with less than 10% error across all classes except for lower SAV growth forms in the most turbid waters. In light of these results, we conclude that it is possible to monitor SAV distribution using high-resolution remote sensing within an open-sourced environment with a flexible and functional workflow.

Sex-specific thermal tolerance limits in the ditch shrimp Palaemon varians: Eco-evolutionary implications under a warming ocean.

As global temperatures continue to rise due to global change, marine heatwaves are also becoming more frequent and intense, impacting marine biodiversity patterns worldwide. Organisms inhabiting shallow water environments, such as the commercially relevant ditch shrimp Palaemon varians, are expected to be the most affected by rising temperatures. Thus, addressing species' thermal ecology and climate extinction-risk is crucial to foster climate-smart conservation strategies for shallow water ecosystems. Here, we estimated sex-specific upper thermal tolerance limits for P. varians via the Critical Thermal Maximum method (CTmax), using loss of equilibrium as endpoint. We further calculated thermal safety margins for males and females and tested for correlations between upper thermal limits and shrimps' body size. To determine sex-biased variation in P. varians' traits (CTmax, weight and length), we compared trait variation between females and males through the coefficient of variation ratio (lnCVR). Females displayed an average CTmax value 1.8% lower than males (CTmaxfemales=37.0°C vs CTmaxmales=37.7°C). This finding may be related to the larger body size exhibited by females (156% heavier and 39% larger than males), as both length and weight had a significant effect on CTmax. The high energetic investment of females in offspring may also contribute to the differences recorded in thermal tolerance. Overall, organisms with a smaller body-size displayed a greater tolerance to elevated temperature, thus suggesting that smaller individuals may be positively selected in warmer environments. This selection may result in a reduction of size-at-maturity and shifts in sex ratio, given the sexual dimorphism in body size of shrimps. The thermal safety margin of P. varians was narrow (∼2.2°C for males and ∼1.5°C for females), revealing the vulnerability of this species to ocean warming and heatwaves.

Projection of the Global Distribution of Shallow Water Ecosystems and CO2 Flux

Projection of the Global Distribution of Shallow Water Ecosystems and CO2 Flux