Mesoscale features within the Gulf of Mexico (GOM) are known to influence zooplankton dynamics. Here we describe the composition of the zooplankton assemblage off shelf during summer in relation to environmental conditions, with emphasis on hyperiid amphipods and salps. Zooplankton samples were collected in summer of 2015 and 2016 in the central and southern GOM and in the Yucatan Channel in 2015. Two anticyclonic gyres were present in the north and less intense coupled cyclonic-anticyclonic gyres in the south. Zooplankton abundances differed temporally and spatially. Copepods were the dominant group (>55% of total abundance), while several less abundant taxa contributed to inter-annual and spatial differences. Amphipods and salps comprised <3% and their abundances were positively correlated. Fifty-six hyperiid and 10 salp species were identified. The dominant amphipod species were: Lestrigonus bengalensis (summer 2015), Anchylomera blossevillei and Primno spp. juveniles (summer 2016). Dominant salp species were Ihlea punctata, Iasis cylindrica and Thalia spp. Lower salp and amphipod species richness and abundance were associated with anticyclonic structures. Spatial and temporal differences were partly associated with symbiotic relationships between the groups. This study supports previous evidence of high spatial and temporal variability in zooplankton abundance in off-shelf waters of the GOM.

The origin and development of the Journal of the Marine Biological Association of the United Kingdom is described on the occasion of the publication of the 100th volume. Papers in the Journal demonstrate how the techniques and approaches to the study of the marine environment have evolved over the 120 years of publication. The early papers provided a baseline description of the marine environment and of marine communities that allowed the effects of later perturbations of the environment to be determined. Both the early papers and the long time series of records have proved to be particularly relevant as marine scientists try to predict the long-term results of climatic and anthropogenic effects on the marine ecosystem. The Journal has now become increasingly international, with most papers coming from outside Europe.

A century or so after the cessation of almost all mining in Cornwall, certain estuaries still have extremely high sediment concentrations of toxic trace metals, particularly copper and arsenic, but also lead and zinc. These high trace metal loadings in the sediments are to a large degree bioavailable to the local infauna, especially sediment-ingesting invertebrates. Some sediment trace metal bioavailabilities are so high as to be of ecotoxicological concern, with deleterious effects on the local biota at levels of biological organization up to and including changed community structure. The estuaries of interest here are those of the Rivers Carnon (Restronguet Creek), Tamar (and Tavy), Gannel, West Looe and Hayle. These estuaries are especially attractive field sites for comparative trace metal ecophysiology and ecotoxicology research for they lack the confounding presence of other anthropogenic contaminants inevitably present in most estuaries in the developed world. The estuaries also offer a range of combinations of different trace metals and a comparative gradient of sediment bioavailabilities of these trace metals.

Contaminants causing sex-altering, endocrine disrupting-like (ED) effects, or otherwise influencing reproduction, have been of growing concern to humans for more than 50 years. They have also been a perturbing, though less well-studied, phenomenon in marine organisms, following the recognition of tributyltin (TBT)-induced imposex and population extinctions in (neo)gastropods in the 1970s. Whilst ED impacts in mammals and fish are characterized by mimicry or antagonism of endogenous hormones by environmental contaminants (acting through Nuclear Receptors which are present in all metazoans) much less is known regarding pathways to effects in invertebrates. Despite the absence of a defined steroidal/mechanistic component, the extent, severity and widespread nature of ED-like manifestations and altered sexual characteristics observed in marine invertebrates gives rise to comparable concerns, and have been a long-term component of the MBA's research remit. The manifestations seen in sensitive taxa such as molluscs and crustaceans confirm they are valuable indicators of environmental quality, and should be exploited in this capacity whilst we seek to understand the pervasiveness and underlying mechanisms. In so doing, invertebrate indicators address aims of organizations, such as the EEA, OECD, UNEP and WHO, charged with management and monitoring of chemicals and ensuring that adverse effects on humans and the environment are minimized (Bergman et al., 2013). In view of the recent general declines in marine biodiversity, and the potential contribution of ED-like phenomena, safeguarding against deleterious effects through increased research which links pollutant exposure with reproductive dysfunction among invertebrates, is seen as a high priority.

Since the mid-1980s, swarms of the rhizostome Rhopilema nomadica have been an annual phenomenon in Israeli Mediterranean coastal waters during the summer months. Despite its annual prominence and the potential impact on food webs and ecosystem services, studies concerning its feeding ecology and its interactions with other biota in the marine food web have not been conducted. During summer 2015 gut contents of 41 R. nomadica were analysed as well as ambient plankton assemblages. More than 60% of the medusae diet was found to consist of microzooplankton <150 μm. Size correlations revealed that larger R. nomadica consumed faster swimming prey while smaller medusae relied more on the slower swimming taxa. The medusan diet reflected most of the ambient plankton taxa, but no statistically significant correlations between the relative abundance in diet and ambient plankton were found. As summer progressed, there was a gradual decrease in both mean medusa bell diameter (from 42.2–16 cm) and integrity of feeding structures. These findings suggest that R. nomadica, at least at the time of its appearance in Israeli coastal waters, may exert less predatory pressure on the plankton than we might otherwise expect.

With over a century of records, we present a detailed analysis of the spatial and temporal occurrence of marine turtle sightings and strandings in the UK and Ireland between 1910 and 2018. Records of hard-shell turtles, including loggerhead turtles (Caretta caretta, N = 240) and Kemp's ridley turtles (Lepidochelys kempii, N = 61), have significantly increased over time. However, in the most recent years there has been a notable decrease in records. The majority of records of hard-shell turtles were juveniles and occurred in the boreal winter months when the waters are coolest in the North-east Atlantic. They generally occurred on the western aspects of the UK and Ireland highlighting a pattern of decreasing records with increasing latitude, supporting previous suggestions that juvenile turtles arrive in these waters via the North Atlantic current systems. Similarly, the majority of the strandings and sightings of leatherback turtles (Dermochelys coriacea, N = 1683) occurred on the western aspects of the UK and the entirety of Ireland's coastline. In contrast to hard-shell turtles, leatherback turtles were most commonly recorded in the boreal summer months with the majority of strandings being adult sized, of which there has been a recent decrease in annual records. The cause of the recent annual decreases in turtle strandings and sightings across all three species is unclear; however, changes to overall population abundance, prey availability, anthropogenic threats and variable reporting effort could all contribute. Our results provide a valuable reference point to assess species range modification due to climate change, identify possible evidence of anthropogenic threats and to assess the future trajectory of marine turtle populations in the North Atlantic.

Generation of ion electrochemical potential differences by primary active transport can involve energy inputs from light, from exergonic redox reactions and from exergonic ATP hydrolysis. These electrochemical potential differences are important for homoeostasis, for signalling, and for energizing nutrient influx. The three main ions involved are H+, Na+ (efflux) and Cl− (influx). In prokaryotes, fluxes of all three of these ions are energized by ion-pumping rhodopsins, with one archaeal rhodopsin pumping H+into the cells; among eukaryotes there is also an H+ influx rhodopsin in Acetabularia and (probably) H+ efflux in diatoms. Bacteriochlorophyll-based photoreactions export H+ from the cytosol in some anoxygenic photosynthetic bacteria, but chlorophyll-based photoreactions in marine cyanobacteria do not lead to export of H+. Exergonic redox reactions export H+ and Na+ in photosynthetic bacteria, and possibly H+ in eukaryotic algae. P-type H+- and/or Na+-ATPases occur in almost all of the photosynthetic marine organisms examined. P-type H+-efflux ATPases occur in charophycean marine algae and flowering plants whereas P-type Na+-ATPases predominate in other marine green algae and non-green algae, possibly with H+-ATPases in some cases. An F-type Cl−-ATPase is known to occur in Acetabularia. Some assignments, on the basis of genomic evidence, of P-type ATPases to H+ or Na+ as the pumped ion are inconclusive.

Ports have long been considered ‘high-risk’ areas for the introduction of non-native species (NNS) and should therefore be a focus of NNS monitoring. The industrial nature of active ports can, however, provide various problems when attempting to carry out monitoring programmes. Current methodologies designed to identify NNS and to describe fouling communities have not been developed specifically for use in active ports and can encounter a number of issues when used in these environments. Here, two surveys were developed and trialled within an active port in South Wales, UK, designed to describe fouling communities, identify NNS and overcome some of the major limitations to conducting surveys within ports. Over a 6-month period, fouling communities dominated by solitary ascidians developed in each survey. Seven NNS were identified, mostly species already recorded in the 1950s, including the Mediterranean crab Brachynotus sexdentatus, and the more recently introduced Japanese skeleton shrimp Caprella mutica. Each survey was evaluated independently with respect to key factors, including the ability to detect NNS and practical aspects of using these survey methods in an applied context. We conclude that whilst each survey can function independently, the use of both survey types in conjunction offers the most robust solution to identifying NNS and describing wider fouling communities within active ports. This research has implications for the future monitoring and management of NNS within UK ports.

Rocky shore ecology has been studied for a long time, starting with qualitative descriptions and becoming more quantitative and experimental over time. Some of the earliest manipulative experimental ecological studies were undertaken on rocky shores. Many, over time, have made considerable contributions to ecological theory, especially highlighting the importance of biological interactions at the community level. The suitability of rocky shores as convenient test systems for ecological experimentation is outlined. Here we consider contributions from rocky shores to the emerging concepts of supply-side ecology, the roles of competition, predation and grazing, disturbance and succession and positive interactions in structuring communities along environmental gradients. We then address alternative stable states, relationships between biodiversity and ecosystem functioning, and bottom-up and top-down control of ecosystems. We briefly consider the feedback and synergies between ecological concepts and experimental work on rocky shores, whilst still emphasizing the traditional values of marine natural history upheld in JMBA since its first publication. The importance of rigorous experimental designs championed by Underwood and co-workers is emphasized. Recent progress taking advantage of new technologies and emerging approaches is considered. We illustrate how experimental studies have shown the importance of biological interactions in modulating species and assemblage-level responses to climate change and informed conservation and management of coastal ecosystems.

Knowledge of bio-physicochemical variables is essential to better understand the functioning of tropical marine ecosystems, which are rich in biodiversity and provide nutrition and livelihoods to billions of people in the developing countries. This study analysed the spatial and temporal variability of phytoplankton and zooplankton with chlorophyll, primary productivity, temperature, salinity, oxygen and nutrients in the Bay of Bengal (BoB), collecting data from the World Ocean, and COPEPOD and Aqua MODIS records. The results indicated a strong gradient in bio-physicochemical conditions of the BoB, from the coast to the open sea. Specifically, the spatial variability in chlorophyll was negatively correlated (R2 = 0.59) with temperature and zooplankton, while a positive correlation (R2 = 0.70) was noted between chlorophyll and silicate, nitrate, phosphate, dissolved oxygen and salinity. All the variables exhibited a strong vertical gradient at depths up to 500 m. Temperature, nutrients, zooplankton and to a lesser extent salinity and rainfall had an influence on the annual abundance of phytoplankton. Over the long term, a significant positive trend in temperature and a significant negative trend in primary productivity were observed in the BoB. The findings of this study will be useful to draw insights on the state of fisheries habitats and the overall environmental conditions of the BoB in response to future climate changes.

The flat oyster Ostrea edulis has declined significantly in European waters since the 1850s as a result of anthropogenic activity. Ostrea edulis was designated a UK Biodiversity Action Plan Species and Habitat in 1995, and as a Feature of Conservation Importance (FOCI) within the UK Marine & Coastal Access Act 2009. To promote the recovery of oyster beds, a greater understanding of its abundance and distribution is required. Distribution of O. edulis across the proposed Blackwater, Crouch, Roach and Colne MCZ in Essex was determined between 2008 and 2012. Ostrea edulis were present in four estuary zones; with highest sample abundance in the Blackwater and Ray Sand zones. Size structure of populations varied, with the Ray Sand and Colne zones showing a significant lack of individuals with shell height <39 mm. Ostrea edulis occurred in highest number on shell substratum, followed by silty sediments. There were no significant associations between O. edulis abundance or size structure with water column Chl a, suspended solids, oxygen, nitrate or ammonium concentrations, temperature or pH. Highest abundance and most equitable population shell-size distribution for O. edulis were located within, or adjacent to, actively managed aquaculture zones. This suggests that traditional seabed management contributed to the maintenance or recovery of the species of conservation concern. Demonstration that the Essex estuaries were a stronghold for Ostrea edulis in the southern North sea area led to the designation of the Blackwater, Crouch, Roach and Colne estuaries Marine Conservation Zone in 2013.

The intertidal coastline of Ceredigion, Wales, comprises a patchwork of unstable sand and cobble beaches, and stable bedrock areas and boulder-fields. The last two shoreline types support rock-pools with growths of the red alga Corallina officinalis, the thalli of which are a popular substrate for calcareous epiphytes. Replicate samples of C. officinalis (four per site) were taken from (a) three bedrock sites (Ceinewydd, Aberystwyth Victoria Rocks and Castle Rocks) and (b) three boulder-fields (Llanon, Aberaeron lower shore (Aberaeron LS), Llanina) on the lower shore. The middle shore boulder field at Aberaeron (Aberaeron MS) was also sampled. These replicates were examined for calcareous meiofauna (63–2000 μm) not previously examined as a community: spirorbids, foraminifera, gastropods, bryozoans, ostracods and ophiuroids. These were assigned to sessile and vagile modes of life. The sessile association overwhelmingly dominated bedrock coastlines and the Aberaeron MS, while the vagile association was at its most abundant on the Corallina from lower shore, stable boulder-fields. Gastropods were almost entirely limited to Corallina on boulder-fields. We hypothesize that the boulders induce low-energy turbulence among breaking waves, allowing the less firmly attached vagile meiofauna to dominate on C. officinalis in rock-pools in lower shore boulder-fields. The small attachment area of sessile organisms allows them to settle bedrock sites in greater densities than do vagile organisms at boulder-field sites, which are presumed to require larger foraging areas.

Structure and diversity of sessile zoobenthic assemblages seem to be driven not only by chemical-physical constraints and biological interactions but also by substrate lithology and its surface features. Nevertheless, broadly distributed crustose epilithic corallines could mask the role of substrate on animal settling. To evaluate the direct influence of different rocky substrates, occurrence and coverage of several sessile species, growing on the dark (i.e. coralline-free) face of sublittoral limestone and granite boulders were compared in the Tavolara MPA (Mediterranean Sea). The analysis of photographic samples demonstrated significant differences in terms of species composition and coverage, according to lithology. Moreover, limestone boulders were widely bare, while the cover per cent was almost total on granite. The leading cause of observed patterns could be the different level of dissolution of the two types of rocks, due to their different mineral composition and textural characteristics. Limestone has previously been shown to have higher dissolution compared with granite, and consequently, a more unstable surface. Our results suggest that, in dark habitats, the absence of the crustose coralline layer allows more rock dissolution and consequent lower stability of the limestone compared with granite, which, in turn, reduces the zoobenthos colonization.