Inshore Waters Research Articles

Evaluating the use of whalewatch data in determining killer whale (Orcinus orca) distribution patterns

Commercial whalewatching has been used as an opportunistic data source for studies of cetacean distribution, but there are few comprehensive analyses of the biases and assumptions implicit in such methodology. The goal of this study was to evaluate the use of data generated by commercial whalewatch operators using a case study of whalewatchers targeting killer whales (Orcinus orca) within Washington and British Columbia inshore waters. In this region, many whalewatch vessels work cooperatively in a small, semi-enclosed area to locate and identify well-known killer whales. To address search biases and cross-examine the accuracy in killer whale locations and pod identifications by whalewatchers, an independent field study was conducted. The whalewatch data were 91.7% accurate in locating killer whales, but only 74.1% of those sightings were correctly identified to the pod level. However, identification accuracy increased to 92.6% when errors due to sub-pod mis-identification were excluded and 96.3% when early morning (before 10:30), unknown pod sightings were also excluded. It is suggested that these data can be used to describe spatial use patterns by killer whales, with recognition of the dataset’s limitations. Results of this study indicate that examination of biases is necessary before initiating research using data generated by commercial whalewatchers, but such data sources can be effective for specific study questions if the limitations are known. Although the whalewatch situation described here is relatively unique because it targets a small, well-known population, this study presents a practical methodology for evaluating the efficiency of whalewatch vessels in detecting and identifying cetaceans. Globally, whalewatching industries are increasing in numbers and geographic scope, and capitalising on these platforms of opportunity represents potentially valuable and accurate data for studies of cetacean distribution.

Marine Ecological Function Zoning and Management Countermeasures: A Case Study of the Sea Area of Zhejiang Province

The contradiction between the development of marine resources and ecological protection in Zhejiang is prominent, which restricts the high-quality and continuous supply of marine ecological products. As a result, the efficient maintenance of the ecological security pattern of inshore waters relies on the scientific division of marine ecological function zones and the management and maintenance of zoning areas. This paper constructs a technical framework for marine ecological function zoning from the aspects of marine ecosystem health, marine ecosystem diversity and economic and social development balance using GIS-based overlay analysis and the three-dimensional matrix discriminant model to divide marine ecological function zones in the managed waters of Zhejiang Province. The results indicate that the managed sea areas in Zhejiang Province are divided into ten marine ecological function areas, including three marine ecological supply areas (54%), four marine mariculture and resting areas (24%) and three marine ecological restoration areas (22%). As per the zoning results of the marine ecological function, this study further proposes protection and management strategies for different zoning units, in the hopes of providing technical support and practical reference for the division and management of marine ecological function areas in other sea areas.

Feeding ecology of broadbill swordfish (Xiphias gladius) in the California current.

The feeding ecology of broadbill swordfish (Xiphias gladius) in the California Current was described based on analysis of stomach contents collected by fishery observers aboard commercial drift gillnet boats from 2007 to 2014. Prey were identified to the lowest taxonomic level and diet composition was analyzed using univariate and multivariate methods. Of 299 swordfish sampled (74 to 245 cm eye-to-fork length), 292 non-empty stomachs contained remains from 60 prey taxa. Genetic analyses were used to identify prey that could not be identified visually. Diet consisted mainly of cephalopods but also included epipelagic and mesopelagic teleosts. Jumbo squid (Dosidicus gigas) and Gonatopsis borealis were the most important prey based on the geometric index of importance. Swordfish diet varied with body size, location and year. Jumbo squid, Gonatus spp. and Pacific hake (Merluccius productus) were more important for larger swordfish, reflecting the ability of larger specimens to catch large prey. Jumbo squid, Gonatus spp. and market squid (Doryteuthis opalescens) were more important in inshore waters, while G. borealis and Pacific hake predominated offshore. Jumbo squid was more important in 2007-2010 than in 2011-2014, with Pacific hake being the most important prey item in the latter period. Diet variation by area and year probably reflects differences in swordfish preference, prey availability, prey distribution, and prey abundance. The range expansion of jumbo squid that occurred during the first decade of this century may particularly explain their prominence in swordfish diet during 2007-2010. Some factors (swordfish size, area, time period, sea surface temperature) that may influence dietary variation in swordfish were identified. Standardizing methods could make future studies more comparable for conservation monitoring purposes.

Population dynamics of killer whales (Orcinus orca) in the Crozet Archipelago, southern Indian Ocean: a mark-recapture study from 1977 to 2002

Population size and annual survival probabilities for the killer whales (Orcinus orca) inhabiting the inshore waters of Possession Island, Crozet Archipelago, southern Indian Ocean, were estimated through mark-recapture modelling. Capture histories were generated from a set of photographs taken under a photo-identification protocol and a set of photographs taken opportunistically, between 1964 and 2002. Photographs were selected according to their intrinsic quality and the degree of natural marking of individuals. Under those conditions, only well-marked individuals were considered as ‘marked’ from a capture-recapture perspective. The purpose of this double selection was to minimise identification errors and reduce the heterogeneity of capture probabilities. Abundance estimates were derived from the Mth sequential model for closed populations and adjusted for the proportion of well-marked individuals in the study population and for the number of photo-identified individuals. Under this framework, estimates of 98 (95% CI 70-156) individuals in 1988-89, and 37 (95% CI 32-62) individuals in 1998-2000 are proposed. After a weighted model averaging, the Cormack-Jolly-Seber models with the strongest support from the data produced low survival probability estimates, decreasing from 0.935 (95% CI 0.817-0.979) to 0.895 (95% CI 0.746-0.961) for males, and from 0.942 (95% CI 0.844-0.980) to 0.901 (95% CI 0.742-0.966) for females over the period 1977-2002. A Jolly-Seber model was used as a ‘second opinion’ model. It confirmed the worrying status of the population with a constant survival probability estimated at 0.89 (95% CI 0.84-0.93) and a constant rate of increase (applying to the well-marked fraction of the population) estimated at 0.94 (95% CI 0.90-0.99) for the period 1987-2000. This rate of increase is consistent with the abundance estimates presented here. Possible violations of the underlying model assumptions were investigated and it was concluded that the abundance estimates for the period 1988-89 and the CJS survival estimates should be the most reliable results. It is feared that the killer whales around Possession Island are in sharp decline, as may be true for the whole Crozet Archipelago. The effect of low prey stocks and lethal interactions with fisheries as the most likely causes of this decline are discussed.

Cetacean distribution and relative abundance in Colombia’s Pacific EEZ from survey cruises and platforms of opportunity

Cetacean sighting data collected under various programmes in Colombian Pacific waters were collated with the goal of assessing the distribution and abundance patterns of all species occurring in the exclusive economic zone (EEZ). Distribution maps are presented for 19 species and one genus based on 603 sightings collected between 1986 and 2008. Ordered by sighting frequency, these species were: humpback whale (Megaptera novaeangliae); striped dolphin (Stenella coeruleoalba); common bottlenose dolphin (Tursiops truncatus); pantropical spotted dolphin (Stenella attenuata); common dolphin (Delphinus delphis); Risso’s dolphin (Grampus griseus); sperm whale (Physeter macrocephalus); rough-toothed dolphin (Steno bredanensis); short-finned pilot whale (Globicephala macrorhynchus); mesoplodont whales (Mesoplodon spp.); Cuvier’s beaked whale (Ziphius cavirostris); melon-headed whale (Peponocephala electra); false killer whale (Pseudorca crassidens); killer whale (Orcinus orca); spinner dolphin (Stenella longirostris); dwarf sperm whale (Kogia sima); Bryde’s whale (Balaenoptera edeni); pygmy killer whale (Feresa attenuata); minke whale (Balaenoptera acutorostrata) and fin whale (Balaenoptera physalus). Concentrations of sightings were observed in three geographic areas: (1) the continental shelf (depths <200m) and the contiguous continental slope (200–2,000m); (2) over the Malpelo Ridge, an offshore bathymetric feature and (3) the northeast corner of the EEZ between Golfo de Cupica and the border with Panamá, although we do not rule out that these patterns could be an artefact of non-random effort. In inshore waters, the most frequently seen species were pantropical spotted dolphin, common bottlenose dolphin and humpback whale. For several of the data sets we provide encounter rates as indices of relative abundance, but urge caution in their interpretation because of methodological limitations and because several factors that affect sightability could not be accounted for in these estimates. Our results provide useful information for ongoing regional research and conservation initiatives aimed at determining occurrence, population status and connectivity within adjacent EEZs in the eastern tropical Pacific. Suggested research priorities include conducting dedicated surveys designed for estimating abundance and monitoring trends throughout the EEZ and focused studies in areas of special interest like the continental shelf, the Malpelo Ridge and the vicinity of Cupica and Cabo Marzo. More research is also needed in terms of quantifying the sources and impact of anthropogenic mortality on population size. Studies characterising genetic diversity and stock discreteness in coastal species (pantropical spotted dolphin and common bottlenose dolphin) would help inform local management strategies.

Democracy and Human Rights in the Management of Small-Scale Fisheries in England

Small-scale fisheries (SSF) in England face several challenges to their viability. We argue that the source of these challenges can be traced to the more dominant large-scale fisheries (LSF) sector which has more influence than SSF over government policies. A recent attempt to mitigate the impact of these challenges has been made by the Future of Inshore Fisheries initiative whose main prescription is co-management, i.e., giving SSF a participatory role with the government and LSF in the decision-making in English fisheries management. Co-management is a form of democracy and it may help the SSF to deal with their problems. However, in our view, the English SSF also require an acknowledgement of their human rights to a fair quota and protected access to productive inshore waters. In making this case, we draw on normative arguments to assert that human rights are prior to democratic processes. Our conclusion is that both democratic decision-making and human rights principles are needed to secure the English SSF from the real threat of extinction.

Interactions of bioactive trace metals in shipboard Southern Ocean incubation experiments

AbstractIn the Southern Ocean, it is well‐known that iron (Fe) limits phytoplankton growth. Yet, other trace metals can also affect phytoplankton physiology. This study investigated feedbacks between phytoplankton growth and dissolved Fe, manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and cadmium (Cd) concentrations in Southern Ocean shipboard incubations. Three experiments were conducted in September–October 2016 near the West Antarctic Peninsula: Incubations 1 and 3 offshore in the Antarctic Circumpolar Current, and Incubation 2 inshore in Bransfield Strait. Additions of Fe and/or vitamin B12 to inshore and offshore waters were employed and allowed assessment of metal (M) uptake relative to soluble reactive phosphorus (P) across a wide range of initial conditions. Offshore, treatments of >1 nmol L−1 added Fe were Fe‐replete, whereas inshore waters were already Fe‐replete. Results suggest Mn was a secondary limiting nutrient inshore and offshore. No Fe‐vitamin B12 colimitation was observed. Overall, M:P uptake in the incubations was closely related to initial dissolved M:P for Fe, Mn, Co, Ni, and Cd, and for Cu inshore. Final concentrations of Fe and Zn were similar across light treatments of the experiments despite very different phytoplankton responses, and we observed evidence for Co/Cd/Zn substitution and for recycling of biogenic metals as inventories plateaued. In dark bottles, the absence of Mn oxidation may have allowed more efficient recycling of Fe and other trace metals. Our results provide insight into factors governing trace metal uptake, with implications for phytoplankton community composition locally and preformed micronutrient bioavailability in Southern Ocean water masses.

Shoreline change due to global climate change and human activity at the Shandong Peninsula from 2007 to 2020

In this study, how shoreline change responses to global climate change and human activity at the Shandong Peninsula was quantified by analyzing shoreline locations, inshore erosion/accretion rates, and sandy beach profiles for 2007–2020. During the study period, the total shoreline length decreased from 3345.55 km to 3310.18 km, whereas the natural shoreline decreased by 25.41%. As a dominant shore type, the artificial shoreline increased by 827.89 km. Human activities, such as land reclamation and harbor construction, have caused continuous shoreline advance, resulting in a net land increase of 672.40 km2. However, natural shores (e.g., sandy shore) receded at an average annual rate of −1.0 m due to ongoing erosion. The inshore waters of the Shandong Peninsula were largely sedimentary as erosion occurred only at a few hotspots. Therefore, seaward sediment deposition dominated the erosion/accretion trends of the inshore areas of the peninsula. However, global climate change and human activities have exacerbated the erosion caused by sea level rise. Specifically, the climate change caused absolute sea level rise and increasing frequency of extreme weather events, whereas the human activity dominated the transport and supply of sediment in the coastal zone. In the short term, the shoreline of the Shandong Peninsula continues to advance toward the sea due to the growing artificial shoreline. However, this disrupts the balance between sediment supply and marine energies in the coastal zone, and the system then rebalance itself by eroding unprotected natural shores. In the long term, main shoreline evolution trends depend on global climate change and sea level rise which plays a decisive role in shoreline retreat in the Shandong Peninsula.

About Unprovoked Shark Attacks at Pernambuco’s Inshore Waters

Unprovoked shark attacks have suddenly started at Pernambuco’s inshore waters from 1990s onwards. Some studies have pointed out different hypotheses to explain the reasons for this anomaly in the coast of Pernambuco. However, inconsistencies concerning some of these hypotheses indicate the need of further investigations to clarify which environmental and anthropic factors are driving such abnormal incidents with sharks in the south coast of Pernambuco.

Drivers of the spatial behaviour of the threatened thornback skate (Raja clavata)

Fish movements are fundamental to their ecology and survival. Understanding the causes and consequences of the spatial behaviour of fish is of high relevance as it provides critical knowledge for conservation purposes. Skate (Rajidae) populations face an unprecedented global decline due to overfishing. In this study, we used acoustic telemetry to track the movements of nine individuals of the near threatened thornback skate (Raja clavata) around the Cíes Islands, a small marine protected area in the northwest of the Iberian Peninsula. Our results demonstrate the significant impacts of biotic and abiotic drivers on the spatial behaviour of R. clavata. Overall residency inside the study array was low (0.073), differed between sexes (higher for females) and over the course of the year (peaking in summer). The analysis of the direction of the excursions performed by R. clavata individuals revealed high consistency in the exit and entry areas and a strong connectivity with inshore waters connecting with the Ría de Vigo, as compared with offshore waters connecting with the open ocean. Finally, the activity space of R. clavata also varied over the time of the year with a peak in summer. This study provides an important baseline information for understanding the spatial behaviour of R. clavata that can serve as a starting point for planning future conservation actions or studies.

Thermal stress gradient causes increasingly negative effects towards the range limit of an invasive mussel

Environmental filtering (EF), the abiotic exclusion of species, can have first order, direct effects with cascading consequences for population dynamics, especially at range edges where abiotic conditions are suboptimal. Abiotic stress gradients associated with EF may also drive indirect second order effects, including exacerbating the effects of competitors, disease, and parasites on marginal populations because of suboptimal physiological performance. We predicted a cascade of first and second order EF-associated effects on marginal populations of the invasive mussel Mytilus galloprovincialis, plus a third order effect of EF of increased epibiont load due to second order shell degradation by endoliths. Mussel populations on rocky shores were surveyed across 850 km of the south–southeast coast of South Africa, from the species' warm-edge range limit to sites in the centre of their distribution, to quantify second order (endolithic shell degradation) and third order (number of barnacle epibionts) EF-associated effects as a function of along-shore distance from the range edge. Inshore temperature data were interpolated from the literature. Using in situ temperature logger data, we calculated the effective shore level for several sites by determining the duration of immersion and emersion. Summer and winter inshore water temperatures were linked to distance from the mussel's warm range edge (our proxy for an EF-associated stress gradient), suggesting that seasonality in temperature contributes to first order effects. The gradient in thermal stress clearly affected densities, but its influence on mussel size, shell degradation, and epibiosis was weaker. Relationships among mussel size, shell degradation, and epibiosis were more robust. Larger, older mussels had more degraded shells and more epibionts, with endolithic damage facilitating epibiosis. EF associated with a gradient in thermal stress directly limits the distribution, abundance, and size structure of mussel populations, with important indirect second and third order effects of parasitic disease and epibiont load, respectively.

Breeding Thin-Billed Prions Use Marine Habitats Ranging from Inshore to Distant Antarctic Waters.

Pelagic seabirds cover large distances efficiently and thus may reach a variety of marine habitats during breeding. Previous studies using stable isotope data and geolocators suggested that Thin-billed Prions breeding in the Falkland Islands in the Southwest Atlantic may forage in temperate waters over the Patagonian Shelf or cross the Drake Passage to forage in Antarctic waters south of the Polar Front. We deployed miniature GPS dataloggers to track Thin-billed prions in the Falkland Islands during incubation (3 seasons) and chick-rearing (2 seasons). Thin-billed Prions had a wide distribution during incubation, covering latitudes between 43 and 60° S, with trip lengths of ca. 2000 km over seven days, on average. Thin-billed Prions from two nearby sites (60 km apart) were spatially segregated in their incubation trips, with New Island Thin-billed Prions foraging over the Patagonian Shelf, compared to Thin-billed Prions from Bird Island, that foraged in the region of the Polar Front. During chick-rearing, Thin-billed Prions from New Island undertook both long trips to the Patagonian Shelf and south of the Polar Front (30% of trips were 5-11 days), and short trips (70% of trips were 1-4 days) when they foraged more locally, including in inshore waters around the Falkland Islands. Females carried out more trips to distant sites. Thus, Thin-billed showed a high flexibility in foraging areas, habitats and foraging trip durations, which enable them to benefit from both, temperate and Antarctic environments.

Novel insights into the spatial genetic patterns of the finless porpoise from East to Southeast Asia

Several cetacean species are endemically distributed throughout the Indo-Pacific. Due to disproportionate sampling and research efforts across the Indo-Pacific region, the spatial genetic structure of these species remains poorly understood. This has led to poor phylogeographic knowledge and ambiguous taxonomic classification of many Indo-Pacific cetacean species. Of these, the finless porpoise (genus Neophocaena) is a small cetacean obligatory to the inshore waters from East Asia to the Persian Gulf of the Indian Ocean. To date, two species are generally recognized: the narrow-ridged finless porpoise inhabiting temperate and subtropical waters, and wide-ridged finless porpoises inhabiting subtropical and tropical waters. Early research efforts focused on the temperate waters off the northern China. However, recent studies have proposed that the primary divergence within the genus may lie between the Indian Ocean and Pacific region, which remains to be tested with more samples from tropical and subtropical regions. Here, we examined the genetic relationship among the finless porpoises from the Gulf of Thailand to the Taiwan Strait using both mitochondrial and autosomal markers. Bayesian assignment analysis suggested a minimum of four genetic populations within the study areas, corresponding to the narrow-ridged finless porpoise from the Taiwan Strait (TWSn), and the three wide-ridged finless porpoise populations from the Taiwan Strait (TWSw), Pearl River Delta region (PRDw), and the Gulf of Thailand (Thaiw), respectively. The minimum spanning network of the mtDNA control region found shared haplotypes among finless porpoises in Chinese waters, but those from the Gulf of Thailand formed a unique matriline lineage. Consistently, the genetic differentiation or divergence within the South China Sea (Thaiw vs. PRDw) appears to be higher than that of most finless porpoise populations examined to date, and meets the threshold values of species or sub-species level proposed for the cetacean species. The Mantel test detected a strong correlation between the geographic and genetic matrices within the South China Sea (r ​> ​0.99, p ​< ​0.001), indicating that the divergence associated with isolation-by-distance (IBD) has been accumulating in recent history. Our results imply that the formation and maintenance of the spatial genetic pattern of the finless porpoise is more complex than previously thought. However, this cannot be addressed by the current taxonomic classification of the genus.

Developing species distribution models for critically endangered species using participatory data: The European sturgeon marine habitat suitability

Increasing knowledge on distribution and habitat selection of coastal fish species is essential for the management of marine environments, and can be provided through the use of Species Distribution Models (SDM). Opportunistic and participatory data, such as recreational or commercial bycatch data, can provide precious information at large scale and low cost to estimate fish spatial distributions, but are subject to biases (e.g. lack of absence data, non-random sampling scheme). The European sturgeon (Acipenser sturio) is a critically endangered diadromous fish and its marine habitat preferences are unknown. The goal of this study was to investigate key variables driving A. sturio distribution and predict its current distribution in inshore waters along the European Atlantic coast. We developed two correlative SDM in A. sturio marine habitats based on incidental observations (2012–2021) and two different sets of environmental predictors. In both attempts, six methods which differ according to the biases they aim to reduce (i.e. oversampled areas or environmental conditions, dependence between calibration and validation datasets) and the input dataset used (i.e. random pseudo-absences or target-group pseudo-absences) were applied at various stages of the model building and evaluation process. By comparing potentially biased and bias-corrected predictions, we found similar satisfactory level of evaluation and spatial patterns of habitat suitability. Marine areas predicted as the most suitable were distributed along the French Atlantic coast, the Seine and Somme bays, and at a lesser extent around the Rhine delta and in some coastal areas of the Cantabrian Sea (Northern Spain). We found a strong influence of the bathymetry, temperature, and salinity as well as an influence of the bottom current velocity and of the distance to the source population in explaining A. sturio marine distribution, while the nature of the substrate was not retained by the models. Results of this study could pave the way toward more integrated conservation measures for this critically endangered fish.

Feeding ecology of an inshore population of Notothenia coriiceps from the Argentine Islands, Bellingshausen Sea

The inshore waters off the Argentine Islands host a diversified benthic fish community largely dominated by the black rockcod, Notothenia coriiceps. Compared to other areas along the western Antarctic Peninsula, the feeding habits of this species in this location are poorly known. Hence, the aim of the study is to assess food preferences by the stomach content examination, applying a sophisticated analytical approach. As reported elsewhere, the black rockcod is omnivorous, relying primarily on algae, gastropods, amphipods, euphausiids and fishes, each consumed with different foraging strategies. Based on multidimensional scaling statistical procedures, fish size and water depth are the primarily contributers to prey resource diversification and partitioning. Overall the sampled population of the black rockcod are generalist feeders with a relatively high between-phenotype component to the niche width, consisting of specialized individuals with little or no overlap in food resource use.

An improved fusion method for detecting upwelling off the coast of northwest Africa from chlorophyll-a and sea surface temperature satellite images

ABSTRACT In this letter, a novel method is proposed for extracting upwelling along the Moroccan Atlantic coast using the fusion of satellite observations of biological and physical parameters during the time period 2000–2016. The developed approach first adopted a pre-processing step based on the interpolation to predict the missing values of pixels affected by clouds. Then, three fusion methods defined in the literature were applied to the corrected data to provide three different classifications to each satellite image. The majority voting method was investigated for combining the three classified images and therefore having one fused result more informative than the inputs and detecting well the productive, cold inshore waters. The performance of our procedure is compared to a popular fusion method used to identify upwelling and is evaluated by an index of validation over 769 weekly sea surface temperature ‘SST’ and 769 eight-day chlorophyll-a ‘chl-a’ images. The findings show the robustness of our proposed approach versus the latter method in terms of segmentation accuracy and computational efficiency. Developing on the proposed approach, the spatial and temporal variations of the main physical and biological upwelling patterns are studied.

Quantifying Cross-Shelf Transport in the East Australian Current System: A Budget-Based Approach

Abstract Cross-shelf transport plays an important role in the heat, salt, and nutrient budgets of the continental shelf. In this study, we quantify cross-shelf volume transport and explore its dynamics within a high-resolution (2.5–6 km) regional ocean model of the East Australian Current (EAC) System, a western boundary current with a high level of mesoscale eddy activity. We find that the largest time-mean cross-shelf flows (&gt;4 Sv per 100 km; 1 Sv ≡ 106 m3 s−1) occur inshore of the coherent western boundary current, between 26° and 30°S, while the strongest time-varying flows occur in the EAC southern extension, poleward of 32°S, associated with mesoscale eddies. Using a novel diagnostic equation derived from the momentum budget we show that the cross-shelf transport is dominated by the baroclinic and geostrophic component of the velocities, as the EAC jet is relatively free to flow over the variable shelfbreak topography. However, topographic interactions are also important and act through the bottom pressure torque term as a secondary driver of cross-shelf transport. The importance of topographic interaction also increases in shallower water inshore of the coherent jet. Downstream of separation, cross-shelf transport is more time-varying and associated with the interaction of mesoscale eddies with the shelf. The identification of the change in nature and drivers of cross-shelf transport in eddy versus jet dominated regimes may be applicable to understanding cross-shelf transport dynamics in other boundary current systems. Significance Statement Cross-shelf transport, i.e., the movement of water from the open ocean on or off the continental shelf, is not reported often as it is difficult to measure and model. We demonstrate a simple but effective method to do this and, using an ocean model, apply it to the East Australian Current System and show what drives it. The results show two distinct regimes, which differ depending on which part of the current system you are in. Our results help to place observations of cross-shelf transport in better context and provide a framework within which to consider the transport of other things such as heat and carbon from the open ocean to the continental shelf.

Brown tides linked to the unique nutrient profile in coastal waters of Qinhuangdao, China

Brown tides caused by the pelagophyte Aureococcus anophagefferens have frequently occurred in the Bohai Sea since 2009 and have led to a dramatic collapse of the local scallop culture. To determine why brown tides occurred in the Bohai Sea rather than in other eutrophic coastal waters of China, phytoplankton communities and nutrients were evaluated and nutrient addition experiments were conducted in the Qinhuangdao coastal area. The concentration of dissolved organic nitrogen (DON) was nearly five times higher than that of dissolved inorganic nitrogen (DIN) during brown tides. High levels of phytoplankton biomass and nutrients were observed in the inshore waters, and the patterns of different nutrients were heterogeneous, which could be due to the uneven distribution of pelagophytes and non-brown tide phytoplankton populations (NBTP). The nutrient enrichment results indicated that the growth of the phytoplankton community was nitrogen-limited. Enrichment of DON, especially urea, could promote the growth of pelagophytes during the development stages of the brown tide. In brief, the results of this study imply that the unique nutrient profile (rich in DON but deficient in DIN) could support the outbreak of brown tides in the inshore waters of Qinhuangdao.

Contrasting phytoplankton-zooplankton distributions observed through autonomous platforms, in-situ optical sensors and discrete sampling.

Plankton distributions are remarkably 'patchy' in the ocean. In this study, we investigated the contrasting phytoplankton-zooplankton distributions in relation to wind mixing events in waters around a biodiversity-rich island (Runde) located off the western coast of Norway. We used adaptive sampling from AUV and shipboard profiles of in-situ phytoplankton photo-physiology and particle identification (copepods, fecal pellets and the dinoflagellate Tripos spp.) and quantification using optical and imaging sensors. Additionally, traditional seawater and net sampling were collected for nutrient and in-vitro chlorophyll a concentrations and phytoplankton and meso-zooplankton abundances. Persistent strong wind conditions (~5 days) disrupted the stratification in offshore regions, while stratification and a subsurface chlorophyll maximum (SCM) were observed above the base of the mixed layer depth (MLD ~30 m) in inshore waters. Contrasting phytoplankton and zooplankton abundances were observed between inshore (with the presence of a SCM) and offshore waters (without the presence of a SCM). At the SCM, phytoplankton abundances (Tripos spp., the diatom Proboscia alata and other flagellates) were half (average of 200 cell L-1) of those observed offshore. On the contrary, meso-zooplankton counts were ~6× higher (732 ind m-3 for Calanus spp.) inshore (where a SCM was observed) compared to offshore areas. In parallel, fecal pellets and ammonium concentrations were high (>1000 ind m-3 for the upper 20 m) at the SCM, suggesting that the shallow mixed layer might have increased encounter rates and promoted strong grazing pressure. Low nutrient concentrations (< 1μM for nitrate) were found below the MLD (60 m) in offshore waters, suggesting that mixing and nutrient availability likely boosted phytoplankton abundances. The size of the absorption cross-section (σPII') and yield of photosystem II photochemistry under ambient light (φPII') changed according to depth, while the depth-related electron flow (JPII) was similar between regions, suggesting a high degree of community plasticity to changes in the light regime. Our results emphasize the importance of using multiple instrumentation, in addition to traditional seawater and net sampling for a holistic understanding of plankton distributions.

Metabolomic disorders unveil hepatotoxicity of environmental microplastics in wild fish Serranus scriba (Linnaeus 1758)

Coastal areas are worldwide subject to large inputs of anthropogenic wastes that are discharged directly into inshore waters, where they will be weathered into small microplastics (MPs) of up to a size <20 μm. This study provides information about the presence of small environmental MPs (≤3 μm) in the liver of adult benthopelagic fish Serranus scriba (Linnaeus 1758), caught from three coastal regions in Tunisia distinguished by different patterns of human activity. Polymer composition in fish liver was identified using Raman microspectroscopy. Results revealed differences in the abundance, size distribution and presence of plastic additives over the investigated sites. Polyethylene-vinyl acetate (PEVA: 34% particles/g of tissue), high density polyethylene (HDPE: 24.4%) and the two smaller size classes, i.e. 3-1.2 μm and 1.2-0.45 μm, were the most abundant MPs types and size distribution found, respectively, in Bizerte channel (BC) site (Bizerte city, Tunisia). Moreover, at hepatic level data showed a significant site-dependent cytotoxicity expressed by changes in malondialdehyde (MDA) content, presence of reactive oxygen species (ROS) expressed by altered level of catalase (CAT) and glutathione-S-transferase (GST) activities and in the content of metallothioneins (MTs), as well as genotoxicity by changes in the amount of micronucleus (MN), and neurotoxicity by altered activity of acetylcholinesterase (AChE). A innovative metabolomics analysis was also performed to further investigate the distinct patterns of key metabolite changes in the liver of Serranus scriba. A total of 36 metabolites were significantly affected, mainly involved in energy, amino acid and osmolyte metabolism. These findings emphasised for the first time a close relationship between the source, abundance and size ranges of environmental MPs ≤ 3 μm and their hepatotoxicity in wild organisms.