Oceanographic Variables Research Articles

Temporal oceanographic variation using satellite imagery data in the central Mexican Pacific convergence zone

The oceanographic variation of the central Mexican Pacific (CMP) is mainly driven by the California Current and the Mexican Coastal Current, which generate a convergence zone. Little information is available regarding changes in oceanographic variables at the mesoscale level in the CMP. Therefore, this study characterized 6 oceanographic variables (sea surface temperature, chlorophyll concentration [Chl], primary productivity [PP], diffuse attenuation coefficient [K490], and particulate inorganic/organic carbon concentration [PIC, POC]) in the CMP from 2010 to 2017 and their relationships with El Niño/Southern Oscillation (ENSO). The variables were standardized to monthly pixel values of 0.08 latitude degrees, and the study area covered 48,846.48 km2. Friedman tests were used to compare the temporal variation in the variables, while Spearman correlations were used to evaluate the relationship between each variable and the Multivariate ENSO Index (MEI). A cross-correlation analysis was performed to determine the temporal lag between the oceanographic variables and the MEI. The cyclicity of the variation in the CMP was determined by spectral analysis. All variables showed significant differences between months and years. Two seasons defined by temperature were also detected: a cold season (December–June), in which high values of these variables were observed, and a warm season (July–November), in which low values of these variables were observed. No variables were correlated with the MEI; however, a 4-month time lag was identified between the variables and the MEI. The cyclicity of the variables corresponded to the cold and warm seasons. The cold phase of ENSO increased the values of PP, Chl, and K490 up to 4 times compared to those of other years. Taken together, the observed variation in oceanographic conditions makes the CMP one of the most dynamic coastal regions of the Mexican Pacific.

Multiproxy reconstruction of late quaternary upper ocean temperature in the subtropical southwestern Atlantic

Paleoceanographic studies addressing the oceanographic variability in the western sector of the subtropical South Atlantic - especially those focused on the Brazil Current (BC) and on a time scale that reaches marine isotope stage (MIS) 5 - are still rare when compared with equivalent studies carried out in the Northern Hemisphere. In order to close the data gap prior to the last 75 ka, in an unprecedented approach in this region, we reconstructed the upper temperature variations in the Subtropical Southwestern Atlantic (SSWA) between late MIS 6 and the onset of MIS 4 from organic proxies, using a marine sediment core (GL-1090). Sea temperature records derived from alkenone-based U37K’ and isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs)-based TEX86H proxies were compared with those previously obtained from the same core via Globigerinoides ruber (G. ruber) Mg/Ca and planktonic foraminifera Modern Analog Technique (MAT). The temporal variations of the temperature estimates derived from the U37K′ and TEX86H indexes showed similar patterns, even though the absolute U37K′ temperatures were systematically lower than those derived from TEX86H. Such a difference was related to the different habitat depths of alkenones and isoGDGTs source organisms of – haptophyte algae and marine Thaumarchaeota, respectively. The temperature estimates from TEX86H match the range of Mg/Ca and MAT-derived temperatures between 0 and 10 m depth, suggesting that these proxies reflect mixed layer temperatures. In contrast, the temperature estimates derived from U37K′ were close to the MAT values at between 0 and 100 m and to those derived from TEX86H between 0 and 200 m depth, demonstrating that the U37K′ proxy recorded temperatures from the upper thermocline. During MIS 5e, the difference in temperature estimates from TEX86H and U37K′ was reduced due to more prominent warming, probably related to a change in the thermal structure of the photic zone. Comparison of our data with studies of intensity and salinity anomalies of the Agulhas Current indicates a connection between the intensification of the Agulhas Leakage and the heat storage in the upper thermocline in the SSWA during MIS 5e. Our data suggest that the joint use of TEX86H and U37K′ is a promising approach to estimating paleoceanographic changes in the upper thermocline.

Ensemble modeling of black pomfret (Parastromateus niger) habitat in the Taiwan Strait based on oceanographic variables.

The location, effort, number of captures, and time of fishing were all used in this study to assess the geographic distribution of Parastromateus niger in the Taiwan Strait. Other species distribution models performed worse than generalized linear models (GLMs) based on six oceanographic parameters. The sea surface temperature (SST) was between 26.5 °C and 29.5 °C, the sea surface chlorophyll (SSC) level was between 0.3-0.44 mg/m3, the sea surface salinity (SSS) was between 33.4 °C and 34.4 °C, the mixed layer depth was between 10 °C and 14 °C, the sea surface height was between 0.57 °C and 0.77 °C, and the eddy kinetic energy (EKE) was between 0.603 °C. According to the statistical findings, SST is merely a small effect compared to SSS, SSC level, and EKE in terms of impacting species distribution. By combining four effective single-algorithm models with no obvious bias, an ensemble habitat model was created. The ranges of 117°E-119°E and 22°N-24°N have the highest annual distributions of S.CPUE and nominal CPUE.

Redox conditions and ecological resilience during Oceanic Anoxic Event 2 in the Western Interior Seaway

Oceanic Anoxic Events (OAEs) are important geological events that may be analogues to future climate-driven deoxygenation of our oceans. Much of the global ocean experienced anoxic conditions during the Cenomanian–Turonian OAE (OAE2; ∼94 Ma), whereas the Western Interior Seaway (WIS) experienced oxygenation at this time. Here, organic geochemical and palynological data generated from Cenomanian–Turonian age sediments from five sites in the WIS are used to investigate changing redox and ecological conditions across differing palaeoenvironments and palaeolatitudes. Heterogeneity across the sites is apparent, but important relationships and trends among oceanographic variables are recognised: 1) Increasing total organic carbon (TOC) and CaCO3 percentages indicate the onset of a sea-level maximum towards the end of OAE2; 2) C28 sterane is shown to be a useful marker for prasinophyte abundance, and concurrent increases in this marker and overall sterane abundance indicate prasinophyte-driven increase in algal productivity in a stratified water column; and 3) sterane ratios can be a more reliable geochemical proxy than redox proxies for assessing the Benthic Oxic Zone. Our redox data do not always follow established trends for the WIS overall, particularly for proximal settings. We therefore surmise that local effects, such as nutrient-driven expansion of the oxygen minimum zone and/or sedimentation-driven anoxia just below the sediment-water interface, have overprinted regional trends.

Mesoscale eddies modulate the dynamics of human fishing activities in the global midlatitude ocean

AbstractFrequent fishing activities are causing overfishing, destroying the habitat of marine life, and threatening global marine biodiversity. Understanding the dynamics of fishing activities and their drivers is crucial for designing and implementing effective ocean management. The fishing activities in the open sea are reported to be characterized by high spatial variability in local waters; however, it is still unclear whether their high spatial variability is random or regulated by oceanographic variations. Mesoscale eddies are ubiquitous swirling currents that dominate locally biogeochemical processes. Previous case studies presented an ongoing debate regarding how eddies exert impacts on high trophic organisms, which imposes limitations on understanding the dynamics of fishing activities based on the bottom‐top control hypothesis from eddies to fish and fishing activities. By combining global fishing activities from deep learning and oceanic eddy atlases from satellite monitoring, we showed that the spatial variations in fishing activities were closely related to mesoscale eddies in the global midlatitude ocean, confirming that fishing activities primarily targeting tuna, were aggregated in (repelled from) anticyclonic (cyclonic) eddy cores. This eddy‐fishing activity relationship was opposite to satellite‐observed primary production but corresponded well with the temperature and oxygen content in deeper water. By integrating existing evidence, we attribute eddy‐related fishing activities to a reasonable hypothesis that warm and oxygen‐rich deeper water in anticyclonic eddies relieves the thermal and anoxic constraints for diving predation by tuna while the constraints are aggravated in cold and oxygen‐poor cyclonic eddies.

Blue whales track oceanographic variability across spatial and temporal scales

Animals' ability to track variable resources in space and time is critical to their survival in dynamic and changing ecosystems. Understanding populations' behavioral flexibility in response to natural and anthropogenic ecosystem variation requires long-term and detailed measurements of both animal behavior and ecosystem properties. In a series of recent studies, we leverage blue whales' widely-propagating songs to understand their capacity to track ecosystem variability across episodic foraging and seasonal-to-interannual migration scales. By integrating individual and population-level study of singing blue whales, we first identify an acoustic signature of their population-level transition from foraging to migration. Applying this acoustic signature to a six-year study period, we find that blue whales flexibly time their transition to migration to track interannual variability in the phenology of their foraging habitat. Within the foraging season, we further track blue whale behavior via a directional acoustic vector sensor. Using this approach, we find that blue whales maximize access to aggregated prey patches by dynamically tracking fine-scale wind-driven upwelling plumes in space and time. Combined, these findings display blue whales' ability to track oceanographic variability across spatial and temporal scales and suggest mechanisms by which these predators individually and collectively sense their dynamic foraging habitat.

Sperm whale acoustic ecology investigations using Jeffrey Nystuen‘s Passive Aquatic Listeners

When Jeffrey Nystuen invented the Passive Aquatic Listener (PAL) for quantifying rainfall and wind speed using underwater sound spectra, he considered all biological sounds in the recordings as noise. Using this noise data, I built a doctoral thesis, comprised of three published papers. None of this would have happened without Jeff’s continuous encouragement and support. Here, we present results from analyzing (1) five years (2007–2012) of PAL recordings from Ocean Station PAPA (OSP) in the offshore Gulf of Alaska; and (2) 19 months of PAL data from two sites, Pylos and Athos Stations (in the Hellenic Trench and North Aegean Trough respectively), in the Greek Seas, investigating the acoustic ecology of sperm whales (Physeter macrocephalus). Results of the bioacoustic analysis revealed the year-round presence of sperm whales at OSP and the Ionian Sea, with higher detections during the warm seasons. The sperm whale time series from OSP was correlated with in situ and remotely-sensed oceanographic variables to improve our understanding of global-warming-driven changes in the pelagic ecosystem of the NE Subarctic Pacific. Results from the Hellenic Trench emphasize the risk from increased shipping noise and contribute to the conservation efforts for the small, endangered sperm whale population in an understudied region.

Effect of oceanography on broadband acoustic wave propagation in a range dependent shallow water environment

To investigate the effects of oceanographic variability on broadband acoustic wave propagation in shallow water environments, two experiments were carried out on the New England continental shelf region in 2017 and 2022, respectively. Towed sources were used to transmit chirp waveforms over the frequency ranges of 0.5—1.25 kHz and 1.5 – 4.0 kHz on the same acoustic tracks. The broadband acoustic transmissions were received by vertical acoustic arrays with multiple hydrophones. In 2017, the sound speed in the water column was isovelocity while in 2022 the presence of a duct at the depth of 20 m and upward refracting conditions reduced the interaction of acoustic transmissions with the seafloor compared to the experiment in 2017. Experimental observations show the importance of the water column on bottom interacting broadband waveforms causing challenges for the inversion algorithms. In this paper, we present acoustic and oceanographic results showing how the variability of sound speed could change the characteristics of the broadband transmission. Modeled results versus experimental data are discussed. [Work supported by ONR.]

Modelling relationships between fisheries landings and oceanographic variables: A case study in adjacent areas of Gibraltar Strait

Small pelagics are one of the most important groups of fishes in the world due to their ecologic significance in the trophic web. Small pelagics are the main target of the world’s fishery industry and European anchovy, European sardine, mackerel and horse mackerel represent 43.7% of the total landings in Andalusia (southern Spain). The main objective of this study was to analyse the different factors that could be affecting the abundance of these small pelagics in the two main andalusian fishing areas: Gulf of Cadiz and North Alboran Sea. For this purpose, multiple Generalised Additive Models (GAM) were performed using different oceanographic variables and landing time series as explanatory variables. The explanatory variables were also included with up to a three-year lag. A total of 4776 partial models were performed and eight models (the best for each species per area) were extracted for analysis. GAM models explained up to 61% of the total variance. Most of the models showed a strong non-linear relationship between different fish landings, and all models showed primary production as a key environmental factor to explain variations in the abundance of these small pelagics. However, results also revealed differences in the fishing pressure for all species in both fishing grounds. The use of non-linear models as an analytic tool could be useful for improving the knowledge on small pelagics and the management of the small pelagics fishing industry.

Distribution and densities of fish larvae species with contrasting life histories as a function of oceanographic variables in the deep-water region of the southern Gulf of Mexico.

We describe the larval occurrence and density of six fish species with contrasting life histories and examine their relationships with oceanographic variables during two seasons in the deep-water region (> 1000 m) of the southern Gulf of Mexico based on 12 cruises (2011-2018). Given that Caranx crysos adults are neritic, larval presence close to the continental shelf indicates offshore cross-shelf transport to oceanic waters, which likely leads to mortality. Generalized additive models indicated that C. crysos density was not related with oceanographic variables, while Auxis spp. (with neritic and oceanic adults) was related to wind speed, sea surface temperature, sea surface height, and surface chlorophyll a. The mesopelagic Benthosema suborbitale, Notolychnus valdiviae and Bregmaceros atlanticus were more abundant and broadly distributed, and higher density was found in conditions indicative of higher nutrient availability and productivity, suggesting greater feeding success and survival. The distribution of the epi- and mesopelagic Cubiceps pauciradiatus extended through the southern Gulf of Mexico, and was related to wind speed, sea surface temperature, stratification and chlorophyll a. Our results suggest that the density of the neritic species in oceanic waters could be mediated by regional cross-shelf transport, while for oceanic species is linked with productivity.

Reconstruction Methods in Oceanographic Satellite Data Observation—A Survey

Oceanographic parameters, such as sea surface temperature, surface chlorophyll-a concentration, sea surface ice concentration, sea surface height, etc., are listed as Essential Climate Variables. Therefore, there is a crucial need for persistent and accurate measurements on a global scale. While in situ methods tend to be accurate and continuous, these qualities are difficult to scale spatially, leaving a significant portion of Earth’s oceans and seas unmonitored. To tackle this, various remote sensing techniques have been developed. One of the more prominent ways to measure the aforementioned parameters is via satellite spacecraft-mounted remote sensors. This way, spatial coverage is considerably increased while retaining significant accuracy and resolution. Unfortunately, due to the nature of electromagnetic signals, the atmosphere itself and its content (such as clouds, rain, etc.) frequently obstruct the signals, preventing the satellite-mounted sensors from measuring, resulting in gaps—missing data—in satellite recordings. One way to deal with these gaps is via various reconstruction methods developed through the past two decades. However, there seems to be a lack of review papers on reconstruction methods for satellite-derived oceanographic variables. To rectify the lack, this paper surveyed more than 130 articles dealing with the issue of data reconstruction. Articles were chosen according to two criteria: (a) the article has to feature satellite-derived oceanographic data (b) gaps in satellite data have to be reconstructed. As an additional result of the survey, a novel categorising system based on the type of input data and the usage of time series in reconstruction efforts is proposed.

The lateral transport of zooplankton explains trophic and taxonomic similarities over the zonal gradient of central Chile

The highly productive upwelling zone in the Southeast Pacific provides inputs of C and N to the oceanic deep-water system via lateral transport, although the quality of this organic matter, the organisms being transported, and the controlling mechanisms are unclear. Here, we assessed whether the taxonomic and trophic structure of zooplankton over more oceanic offshore waters differ from that of zooplankton located in the upwelling zone, along with the characterization of the oceanographic processes and variables associated with the lateral transport. For this, epipelagic, mesopelagic, and bathypelagic zooplankton along with oceanographic variables and particulate organic matter (POM) were analyzed at the upwelling zone and adjacent oceanic stations off Central Chile (27–33°S), some of which were located over the Atacama trench, during September 2016. The community structure of size-fractioned zooplankton (<200 μm, 200–500 μm, 500–1000 μm, 1000–2000 μm, and >2000 μm size classes) was assessed by an automated method, along with the analysis of the isotopic niche computed from their δ 15 N and δ 13 C. The isotope signatures of POM indicated that diatoms contributed mostly to production of new organic C, being the main food source for small-sized zooplankton in coastal waters. The zooplankton community structure differed between the upwelling and oceanic areas, but their isotopic signature showed a large overlap (78%). Satellite-derived geostrophic flow and the depth of the mixed layer appeared as the main factors explaining the homogeneity in the isotopic and biogeochemical signatures of zooplankton between the upwelling zone and offshore waters. Cross-shelf advection is thus suggested as a key process promoting zooplankton export to the deep-water ecosystem, including the ultra-deep Atacama Trench. • The organic matter produced in the upwelling zone can be transported over the Atacama trench by strong offshore advection. • Isotopic niches of zooplankton from the Atacama Trench and the upwelling zone exhibit large overlapping (78%). • The upwelling systems acts as a C subsidiary for the offshore deep-sea ecosystem including the Atacama Trench.

Quantifying the effects of extreme events and oceanographic variability on the spatiotemporal biomass and distribution of two key euphausiid prey species

Euphausiids form a critical component of oceanic food chains and individual species vary in their responses to perturbation events. We aimed to establish if patterns of fine scale oceanographic variability and larger-scale climate events such as marine heatwaves (MHWs) could be linked with spring variability in the biomass of two key forage species in the northeast Pacific Ocean, Euphausia pacifica and Thysanoessa spinifera. To achieve this, we used long-term datasets from the west coast of Vancouver Island Canada, an important commercial fishing area, to first quantify interannual signals of variability in fine-scale oceanographic conditions using multivariate analysis. We then used geostatistical spatiotemporal modelling to quantify the effects on species-specific euphausiid biomass. Oceanographic data showed that the effects of warm events are not always observable, and effects vary across small spatial scales. Warming due to the 2014-2016 MHW was relatively mild on the continental shelf during spring (&amp;lt;1°C above climatology). Spring biomass of euphausiids, particularly E. pacifica, peaked in 2015, and all euphausiid groups analysed (E. pacifica, T. spinifera and total euphausiids) exhibited significant correlations with positive phases of the Pacific Decadal Oscillation. These results have implications for marine predators as euphausiids may act as system stabilisers in the northeast Pacific, thereby potentially increasing ecosystem resilience during extreme events.

The Effect of Short-Term Upwelling Events on Fish Assemblages at the South-Eastern Coast of the Baltic Sea

Multiple stressors, such as overfishing, pollution, climate change, biological invasions etc., are affecting fish communities, and thus can have versatile effects on marine ecosystems and socio-economic activities as well. Understanding the changes in the fish community structure is ecologically and economically important, yet a very complex issue, requiring comprehensive analysis of multiple factors. The role of regional oceanographic variability, namely, coastal upwelling, is often neglected when it comes to the analysis of fish assemblages. In this perspective, we were aiming, for the first time in the Baltic Sea, to assess the upwelling influence on fish communities and fish community-based ecological indices used under Marine Strategy Framework Directive. The study covered a long-term period (2000–2019) for upwelling identified by satellite data analysis and fish gillnet surveys, performed in three distinct locations in the coastal waters of the SE Baltic Sea. Overall, our study revealed that temporal dynamics of fish abundance and community composition were associated with the presence of coastal upwelling. The study outcomes suggest that the fish community was more diverse and a higher number of some fish species was observed before upwelling. During upwelling, there was more evident dominance of 1–2 main marine fish species. Through the changes in fish abundance and species composition upwelling was also responsible for the changes in fish community structure-based indices for marine environment status, i.e., in the majority of the cases a decrease in Trophic, Piscivorous Fish, and Diversity indices were observed. Our study demonstrates that upwelling can affect both, the quantitative and qualitative characteristics of coastal fish communities, therefore, it is important to consider this when predicting shifts in the distribution of fish stocks or assessing environmental status indicators, especially under changing climate. We believe that our approach adds novel information to the study of coastal ecosystems of the Baltic Sea and is important for better management of socio-economic activities in the coastal zone.

Effects of Climate Change on Chlorophyll a in the Barents Sea: A Long-Term Assessment.

The Arctic climate strongly affects phytoplankton production and biomass through several mechanisms, including warming, sea ice retreat, and global atmospheric processes. In order to detect the climatic changes in phytoplankton biomass, long-term variability of chlorophyll a (Chl-a) was estimated in situ with the changes in the surface sea temperature (SST) and salinity (SSS) in the Barents Sea and adjacent waters during the period of 1984-2021. Spatial differences were detected in SST, SSS, and Chl-a. Chl-a increased parallel to SST in the summer-autumn and spring periods, respectively. Chl-a peaks were found near the ice edge and frontal zones in the spring season, while the highest measures were observed in the coastal regions during the summer seasons. SST and Chl-a demonstrated increasing trends with greater values during 2010-2020. Generalized additive models (GAMs) revealed that SST and Chl-a were positively related with year. Climatic and oceanographic variables explained significant proportions of the Chl-a fluctuations, with six predictors (SST, annual North Atlantic Oscillation index, temperature/salinity anomalies at the Kola Section, and sea ice extent in April and September) being the most important. GAMs showed close associations between increasing Chl-a and a decline in sea ice extent and rising water temperature. Our data may be useful for monitoring the Arctic regions during the era of global changes and provide a basis for future research on factors driving phytoplankton assemblages and primary productivity in the Barents Sea.

Predictive Modeling of Eastern Little Tuna (Euthynnus affinis) Catches in the Makassar Strait Using the Generalized Additive Model

The Makassar Strait (MS) is characterized by water mass from the Pacific Ocean and is one of the ITF (Indonesia Throughflow) branches. It carries warm water masses from the Pacific Ocean to the Indian Ocean. This research aims to analyze the relationship between CPUE of Eastern Little Tuna (Euthynnus affinis) and oceanographic variables, likewise predict the fishing area using the Generalized Additive Model (GAM). The research method used is spatial and temporal analysis. The data was used from 2015 to 2020. The data processed were sea surface temperature, chlorophyll-a, salinity, currents, sea level as predictor variables, and Eastern Little Tuna production as a response. Eastern Little Tuna catch data were normalized into Catch per Unit Effort, while the oceanographic data were extracted using ArcGIS. Based on the results of the GAM model, it was found that the model with five variables is the most suitable predictive model, with 16.4% CDE. Salinity is the most influential parameter on the catch of Eastern Little Tuna with a significance value of &lt;2.00 × 10−16 ***. The optimum value for SST is 30–31 °C, chlorophyll-a is 1–2 mg/m3, salinity is 29–30 ppt, current velocity is 0.3–0.5 m/s and sea level is between 0.6–0.7 m. Based on the GAM prediction results, a high CPUE value will be obtained in the southwest monsoon (March to May). Fishing activity carried out in the best season will implement the adoption of harvest control measures.

The intensification of coastal hypoxia off central Chile: Long term and high frequency variability

Hypoxia is a phenomenon where dissolved oxygen (DO) is reduced to levels that are low enough to strongly affect ecological and biogeochemical processes. This occurs within the continental shelf off central Chile (36°S), influenced by seasonal coastal upwelling (Spring-Summer). Monthly measurements of DO and other oceanographic variables in the water column (1997−2021) over the 92 m isobath along with high-resolution and near-surface observations (POSAR buoy), are analyzed to examine incidences of hypoxia and understand the physical and biogeochemical processes modulating DO vertical distribution and its temporal variability. On average, the percentage of the water column with DO levels below 89 (hypoxia) and 22 (severe hypoxia) μmol L−1 reaches 68% (i.e., hypoxic waters are found below 30 m) and 44% (below 50 m depth), respectively, but during the upwelling season, as much as 87% (below 12 m depth) and 81% (below 17 m depth) of the water column exhibits these levels. On the sub-seasonal scale during upwelling season six hypoxic events lasting at least 2 days occur at 10 m depth. There is a strong seasonal correlation between the volume of the seawater presenting hypoxia and upwelling favorable winds. Furthermore, there is a high DO interannual variability partially related to the El Niño Southern Oscillation (ENSO). Over 2 decades, it is estimated that DO concentration in surface and subsurface layers decreases (up to 21 μmol L−1 decade−1) as waters get colder (up to 0.29°C decade−1). Remarkably, the volume of hypoxic and severe hypoxic waters over the shelf has increased more than 2 times since 1997 and shows a significant positive correlation with the upwelling index. These preliminary findings indicate that the increase in local DO consumption is partially associated with upwelling intensification. Given the clear evidence of wind intensification in coastal upwelling ecosystems and thus the increase in hypoxic events, the coastal zone may be highly vulnerable to hypoxia, impacting biological resources and biogeochemical cycles.

ORDENAMENTO DE CURRAIS-DE-PESCA NO LITORAL BRASILEIRO: POSSIBILIDADE OU UTOPIA?

Fishing corrals are fixed gear strategically installed considering oceanographic variables, such as tidal regime, behavior of sea currents, wind dynamics and type of sediment. Considering the historical and socioeconomic importance of the activity for the subsistence of many artisanal fishermen, there is a need to order the activity. In this context, the objective of this work was to propose guidelines for the ordering of fishing pens on the Brazilian coast, considering the installation, operation and deactivation phases. Currently, it is possible to observe traps without adequate signage, in areas held by the owners, even practicing the commercialization of the place without any documentation issued by regulatory bodies. Therefore, the installation must take place from the request for the assignment of public space by the Union for fishing purposes through a free declaratory act, online, with MAPA, under the supervision of an area technician. Subsequently, the environmental agency and the Brazilian Navy must be consulted about a 20-year authorization, renewable for another 20 years, granted by the SPU, based on Decree 10.576/2020 directed at aquaculture. In the operation and deactivation stage, the most important aspect is the inspection by the environmental agencies regarding construction issues, such as geographic location, size of structures, materials used in making, selectivity and signaling of the trap, as well as the removal of the art of fishing. Moreover, the expectation is that this legal norm will reduce the competition of conflicts for the multiple uses of water on the Brazilian coast, mainly in the reduction of accidents involving vessels and fishermen of other modalities, as well as promoting the organization of the activity.

Spatial variation in isotope values of Hector’s dolphins from the north coast of the South Island, New Zealand

The north coast of the South Island, Aotearoa New Zealand, is a region with complex bathymetry and biogeochemistry, where oceanographic variability gives rise to very different local environments at fine scales. This variation also influences the region’s isoscape, providing the ability to assess the fine-scale foraging behaviour of top-level marine predators through isotope analyses. Hector’s dolphin Cephalorhynchus hectori hectori, an endemic coastal dolphin, is resident of the north coast of the South Island, but there is limited information describing its foraging ecology and population dynamics. We analysed carbon and nitrogen stable isotope ratios of skin samples (n = 111) from Golden Bay in the west (n = 14), and Queen Charlotte Sound (n = 41) and Cloudy Bay (n = 56) in the east, to investigate spatial variation in isotope values and niche space, found significant differences between the 2 regions. This is likely driven by a combination of differing prey distributions, underlying oceanographic variability, and varying isotopic baselines that may act as an ecological boundary preventing movement between the 2 regions. The isotopic niche space between the west and east differed, but within the east, Queen Charlotte Sound was a subset of Cloudy Bay. This suggests a common prey source and possible movement of individuals between Queen Charlotte Sound and Cloudy Bay. This research highlights the value of stable isotope analysis to investigate regional-scale variation of top-level marine predators and can provide insight into environmental factors that influence resource use.

Seabird abundances projected to decline in response to climate change in Britain and Ireland

Estimating species’ vulnerability to climate change is a key challenge in conservation. Many seabird species are particularly sensitive to the negative effects of warming and are thus threatened by climate change. We projected seabird abundance in 2050 in Britain and Ireland, an internationally important region for seabirds, under climate change scenario RCP8.5. Our projections were based on fitted relationships between abundance and both climatic (air temperature, precipitation) and oceanographic (sea surface temperature, potential energy anomaly) variables, estimated using a Bayesian hurdle model with spatial random effects. The most consistent responses to environmental variables were negative relationships between species presence or abundance and breeding season maximum terrestrial air temperature. Although data and modelling issues meant that future projections could be made for only 15 of the 25 species and with low predictive power for spatial abundance, predictive power was high for spatial presence and moderate for temporal abundance change. Projections suggest that seabirds will generally fare poorly under climate change in Britain and Ireland, with 10 species projected to decline in abundance by 2050. Variable model fit and projection uncertainty limited confidence, which was generally greater for declines than for increases. Fulmar, puffin and Arctic tern were each projected to decline by over 70% with higher confidence. For a few species, colonisation of new areas may reduce projected losses, but this is potentially limited by low availability of suitable habitat. Projected abundance change was more negative for marine specialists than for generalists. Our findings highlight the vulnerability and conservation needs of seabirds in a changing climate.