Cross-basin and cross-taxa patterns of marine community tropicalization and deborealization in warming European seas.

Ocean warming and acidification, decreases in dissolved oxygen concentrations, and changes in primary production are causing an unprecedented global redistribution of marine life. The identification of underlying ecological processes underpinning marine species turnover, particularly the prevalence of increases of warm-water species or declines of cold-water species, has been recently debated in the context of ocean warming. Here, we track changes in the mean thermal affinity of marine communities across European seas by calculating the Community Temperature Index for 65 biodiversity time series collected over four decades and containing 1,817 species from different communities (zooplankton, coastal benthos, pelagic and demersal invertebrates and fish). We show that most communities and sites have clearly responded to ongoing ocean warming via abundance increases of warm-water species (tropicalization, 54%) and decreases of cold-water species (deborealization, 18%). Tropicalization dominated Atlantic sites compared to semi-enclosed basins such as the Mediterranean and Baltic Seas, probably due to physical barrier constraints to connectivity and species colonization. Semi-enclosed basins appeared to be particularly vulnerable to ocean warming, experiencing the fastest rates of warming and biodiversity loss through deborealization.

Shared and contrasting associations in the dynamic nano- and picoplankton communities of two close but contrasting sites from the Bay of Biscay.

Pico- and nanoplankton are key players in the marine ecosystems due to their implication in the biogeochemical cycles, nutrient recycling and the pelagic food webs. However, the specific dynamics and niches of most bacterial, archaeal and eukaryotic plankton remain unknown, as well as the interactions between them. Better characterization of these is critical for understanding and predicting ecosystem functioning under anthropogenic pressures. We used environmental DNA metabarcoding across a 6-year time series to explore the structure and seasonality of pico- and nanoplankton communities in two sites of the Bay of Biscay, one coastal and one offshore, and construct association networks to reveal potential keystone and connector taxa. Temporal trends in alpha diversity were similar between the two sites, and concurrent communities more similar than within the same site at different times. However, we found differences between the network topologies of the two sites, with both shared and site-specific keystones and connectors. For example, Micromonas, with lower abundance in the offshore site is a keystone here, indicating a stronger effect of associations such as resource competition. This study provides an example of how time series and association network analysis can reveal how similar communities may function differently despite being geographically close.

Climate regime shifts and biodiversity redistribution in the Bay of Biscay.

Global ocean warming, wave extreme events, and accelerating sea-level rise are challenges that coastal communities must address to anticipate damages in coming decades. The objective of this study is to undertake a time-series analysis of climate change (CC) indicators within the Bay of Biscay, including the Basque coast. We used an integrated and flexible methodology, based on Generalized Additive Mixed Models, to detect trends on 19 indicators (including marine physics, chemistry, atmosphere, hydrology, geomorphology, biodiversity, and commercial species). The results of 87 long-term time series analysed (~512,000 observations), in the last four decades, indicate four groups of climate regime shifts: 1) A gradual shift associated with CC starting in the 1980s, with a warming of the sea surface down to 100 m depth in the bay (0.10-0.25 °C per decade), increase in air temperature and insolation. This warming may have impacted on benthic community redistribution in the Basque coast, favouring warm-water species relative to cold-water species. Weight at age for anchovy and sardine decreased in the last two decades. 2) Deepening of the winter mixed layer depth in the south-eastern bay that probably led to increases in nutrients, surface oxygen, and chlorophyll concentration. Current increases on chlorophyll and zooplankton (i.e., copepods) biomass are contrary to those expected under CC scenarios in the region. 3) Sea-level rise (1.5-3.5 cm per decade since 1990s), associated with CC. 4) Increase of extreme wave height events of 16.8 cm per decade in the south-eastern bay, probably related to stormy conditions in the last decade, with impacts on beach erosion. Estimating accurate rates of sea warming, sea-level rise, extreme events, and foreseeing the future pathways of marine productivity, are key to define the best adaptation measures to minimize negative CC impacts in the region.

Diversity and regional distribution of harmful algal events along the Atlantic margin of Europe.

The IOC-ICES-PICES Harmful Algal Event Database (HAEDAT) was used to describe the diversity and spatiotemporal distribution of harmful algal events along the Atlantic margin of Europe from 1987 - 2018. The majority of events recorded are caused by Diarrhetic Shellfish Toxins (DSTs). These events are recorded annually over a wide geographic area from southern Spain to northern Scotland and Iceland, and are responsible for annual closures of many shellfish harvesting areas. The dominant causative dinoflagellates, members of the morphospecies 'Dinophysis acuminata complex' and D. acuta, are common in the waters of the majority of countries affected. There are regional differences in the causative species associated with PST events; the coasts of Spain and Portugal with the dinoflagellates Alexandrium minutum and Gymnodinium catenatum, north west France/south west England/south Ireland with A. minutum, and Scotland/Faroe Islands/Iceland with A. catenella. This can influence the duration and spatial scale of PST events as well as the toxicity of shellfish. The diatom Pseudo-nitzschia australis is the most widespread Domoic Acid (DA) producer, with records coming from Spain, Portugal, France, Ireland and the UK. Amnesic Shellfish Toxins (ASTs) have caused prolonged closures for the scallop fishing industry due to the slow depuration rate of DA. Amendments to EU shellfish hygiene regulations introduced between 2002 and 2005 facilitated end-product testing and sale of adductor muscle. This reduced the impact of ASTs on the scallop fishing industry and thus the number of recorded HAEDAT events. Azaspiracids (AZAs) are the most recent toxin group responsible for events to be characterised in the ICES area. Events associated with AZAs have a discrete distribution with the majority recorded along the west coast of Ireland. Ciguatera Poisoning (CP) has been an emerging issue in the Canary Islands and Madeira since 2004. The majority of aquaculture and wild fish mortality events are associated with blooms of the dinoflagellate Karenia mikimotoi and raphidophyte Heterosigma akashiwo. Such fish killing events occur infrequently yet can cause significant mortalities. Interannual variability was observed in the annual number of HAEDAT areas with events associated with individual shellfish toxin groups. HABs represent a continued risk for the aquaculture industry along the Atlantic margin of Europe and should be accounted for when considering expansion of the industry or operational shifts to offshore areas.

Analysis and modelling of predation on biofilm activated sludge process: Influence on microbial distribution, sludge production and nutrient dosage.

The influence of predation on the biofilm activated sludge (BAS) process is studied using a unified model that incorporates hydrolysis and predation phenomena into the two stages of the BAS system: moving bed biofilm reactor pre-treatment (bacterial-predator stage) and activated sludge (predator stage). The unified model adequately describes the experimental results obtained in a cellulose and viscose full-scale wastewater plant and has been used to evaluate the role and contribution of predator microorganisms towards removal of COD, nutrient requirements, sludge production and microbial distribution. The results indicate that predation is the main factor responsible for the reduction of both nutrient requirements and sludge production. Furthermore, increasing the sludge retention time (SRT) does not influence the total biomass content in the AS reactor of a BAS process in two different industrial wastewater treatments.

'The past is the future of the present': Learning from long-time series of marine monitoring.

Using a long-term (1995-2014) monitoring network, from 51 sampling stations in estuaries and coasts of the Basque Country (Bay of Biscay), the objective of this investigation was to assess the responsiveness of 83 variables in water (18), sediments (27), biota (26), phytoplankton (2), macroinvertebrates (5) and fishes (5) to different human pressures and management actions. We used a total of 3247 series of data to analyse trends of improvement and worsening in quality. In a high percentage of the cases, the management actions taken have resulted in positive effects in the environment, as shown by the trend analysis in this investigation. Overall, much more trends of improvement than of worsening have been observed; this is true for almost all the media and biological components studied, with the exception of phytoplankton; and it applies as well to almost all the stations and water bodies, with the exception of those corresponding to areas with water treatment pending of accomplishment. In estuaries with decreasing human pressures during the period, the percentage of series showing quality improvement was higher (approx. 30%) than those showing worsening of quality (12%). Moreover, in those water bodies showing an increase of pressure, variables which can be considered indicators of anthropogenic effects showed negative trends (quality worsening). On the other hand, some of the variables analysed were more affected by natural variability than by changes in pressures. That was the case of silicate, nitrate and suspended solids, which followed trends correlated to salinity, which, in turn, was related to the rainfall regime during the study period.

An integrated mathematical model for chemical oxygen demand (COD) removal in moving bed biofilm reactors (MBBR) including predation and hydrolysis.

An integrated mathematical model is proposed for modelling a moving bed biofilm reactor (MBBR) for removal of chemical oxygen demand (COD) under aerobic conditions. The composite model combines the following: (i) a one-dimensional biofilm model, (ii) a bulk liquid model, and (iii) biological processes in the bulk liquid and biofilm considering the interactions among autotrophic, heterotrophic and predator microorganisms. Depending on the values for the soluble biodegradable COD loading rate (SCLR), the model takes into account a) the hydrolysis of slowly biodegradable compounds in the bulk liquid, and b) the growth of predator microorganisms in the bulk liquid and in the biofilm. The integration of the model and the SCLR allows a general description of the behaviour of COD removal by the MBBR under various conditions. The model is applied for two in-series MBBR wastewater plant from an integrated cellulose and viscose production and accurately describes the experimental concentrations of COD, total suspended solids (TSS), nitrogen and phosphorous obtained during 14 months working at different SCLRs and nutrient dosages. The representation of the microorganism group distribution in the biofilm and in the bulk liquid allow for verification of the presence of predator microorganisms in the second reactor under some operational conditions.

Phytoplankton composition indicators for the assessment of eutrophication in marine waters: present state and challenges within the European directives.

Several legislations worldwide require assessing the health status of marine ecosystems. In Europe, the Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD) demand the evaluation of the status with the overall objective of achieving at least "Good Status", by 2015 and 2020, respectively. For this purpose, Member States are required to evaluate different biological, physico-chemical and hydro-morphological quality elements (WFD), or qualitative descriptors (MSFD). The assessments of both, the phytoplankton element and the eutrophication descriptor should include several attributes, namely phytoplankton biomass, composition, abundance and blooms. However, few composition-based indicators have been proposed. Principally, phytoplankton still relies on chlorophyll-a concentration measurements, mainly due to the high cost of collecting information on this element and the difficulties establishing significant pressure-impact relationships. This investigation describes the difficulties in the development of a phytoplankton community composition indicator, the state of the art and the main challenges for the future.

Phytoplankton pigments and epifluorescence microscopy as tools for ecological status assessment in coastal and estuarine waters, within the Water Framework Directive.

Inverted microscopy is widespread employed for the analysis of phytoplankton composition within water quality monitoring networks. However, the analysis at the lowest taxonomical level is not always required for ecological status assessment. In addition, inverted microscopy can underestimate the small phytoplankton, and not always distinguish photoautotrophic from heterotrophic cells. In this study, as alternative tools, epifluorescence microscopy and High Performance Liquid Chromatography (HPLC) were employed to characterize phytoplankton communities within waters of different trophic condition. Epifluorescence microscopy confirmed its effectiveness to count the small phytoplankton. Furthermore, significant correlations between nutrients of anthropogenic origin and nanoplankton abundances were found. However, this technique resulted very time-consuming. HPLC together with the CHEMTAX program was more appropriate than inverted microscopy, in terms of cost-effectiveness. Also, the main variability patterns observed in the phytoplankton community structure by HPLC coincided with previous findings in the study area. Nevertheless, a rapid screening at the inverted microscope is recommended.

Implementation of the European Marine Strategy Framework Directive: a methodological approach for the assessment of environmental status, from the Basque Country (Bay of Biscay).

The implementation of the Marine Strategy Framework Directive (MSFD) is directing European marine research towards the coordinated and integrated assessment of sea environmental status, following the ecosystem-based approach. The MSFD uses a set of 11 descriptors which, together, summarise the way in which the whole system functions. As such, the European Commission has proposed an extensive set of indicators, to assess environmental status. Hence, taking account of the large amount of data available for the Basque coast (southern Bay of Biscay), together with a recent proposal for assessment within the MSFD, an integrated environmental status assessment approach is developed (for the first time) in this contribution. The strengths and weaknesses of the method, combined with proposals from the MSFD, are discussed.

Sensitivity comparison of laboratory-cultured and field-collected amphipod Corophium multisetosum in toxicity tests.

The feasibility of using lab-cultured amphipods Corophium multisetosum (Stock 1952) to evaluate the toxicity of contaminants present within marine sediments was studied. This was done by comparing the sensitivity of lab-cultured amphipods in a cadmium toxicity test and to toxic sediment samples, during a 10-days bioassay, with field collected individuals. Different responses were observed between field and cultured individuals. Cadmium test indicated high temporal variability in the LC(50) values of field amphipods (2.40-6.55 mg L(-1)). Sensitivity of cultured amphipods was within the seasonal range of the field individuals (5.81 mg L(-1), LC(50)). However, culture amphipods showed much lower sensitivity in toxic sediment samples. Our results indicate that sensitivity should be determined using a sediment matrix, if the assessment of toxicity is based upon bioassays performed with cultured burrower-amphipods.

Seasonal variability in gonad development in the sea urchin (Paracentrotus lividus) on the Basque coast (southeastern Bay of Biscay).

The main limiting factor to carrying out toxicological bioassays with sea urchin larvae is the restricted period for the availability of viable gametes. Although studies have been undertaken of the reproductive cycle of the sea urchin for several areas of the Bay of Biscay, only limited information exists for the southeasternmost area (the Basque coast). Furthermore, this geographical zone presents some particular environmental conditions, e.g., relatively warm waters. In this study, the gonad state of a population of Paracentrotus lividus, settled on the rocky shores of the city of Donostia-San Sebastian have been monitored. These sea urchins are observed to behave like a typical Atlantic population, with generally high gonad indices and a single yearly main spawning period, between April and May. Further, females show a shorter spawning period than males, becoming the limiting organisms for the availability of larvae.

Induction to maturation of the sea urchin Paracentrotus lividus (Lamarck, 1816) under laboratory conditions.

Laboratory experiments were carried out over two different periods, with the aim of investigating and utilizing the induction to gonadal maturation of the sea urchin Paracentrotus lividus. The final objective was to obtain viable gametes outside the period of natural spawning in the environment; which would allow the utilization of ecotoxicological bioassays with sea urchin larvae at any time of the year. The experiment consisted of maintaining some sea urchins in tanks and providing them with a natural photoperiod, unlimited food and a constant temperature of 20 degrees C. During days 0, 30, 60 and 90, gonads from 15 of these sea urchins were compared with those collected simultaneously in the natural environment. The gametes obtained were used to carry out fecundations, in order to check their viability. The final results obtained were clearly influenced by the gonadal state of the sea urchins at the initial stage of the experiment. The best results were obtained within a time period of 60 days and when the initial gonad index was low.

Using multiple ecosystem components, in assessing ecological status in Spanish (Basque Country) Atlantic marine waters.

The European Water Framework and Marine Strategy Directives relate to the assessment of ecological quality, within estuarine and coastal systems. This legislation requires quality to be defined in an integrative way, using several biological elements (phytoplankton, benthos, algae, phanerogams, and fishes), together with physico-chemical elements (including pollutants). This contribution describes a methodology that integrates all of this information into a unique quality assessment for 51 stations from 18 water bodies, within the Basque Country. These water bodies are distributed into four typologies, including soft-bottom coastal areas and three types of estuaries. For each station, decision trees were used to integrate (i) water, sediment and biomonitor chemical data to achieve an integrated physico-chemical assessment and (ii) multiple biological ecosystem elements into an integrated biological assessment. Depending on the availability of ecological quality ratios or global quality values, different integration schemes were used to combine station assessments into water body assessments on a single scale. Several examples from each element have been selected, to illustrate their responses to different pressures; likewise, to establish how the assessed integrated quality has changed, over time. The results made biological and ecological sense and physico-chemical improvements were often correlated with improvements in the quality of benthos and fishes. These tools permit policy makers and managers to take decisions, based upon scientific knowledge, in water management, regarding the mitigation of human pressures and associated recovery processes.

Investigative monitoring within the European Water Framework Directive: a coastal blast furnace slag disposal, as an example.

The European Water Framework Directive (WFD) establishes a framework for the protection of estuarine and coastal waters, with the most important objective being to achieve 'good ecological status' for all waters, by 2015. Hence, Member States are establishing programmes for the monitoring of water quality status, through the assessment of ecological and chemical elements. These monitoring programmes can be of three types: surveillance monitoring; operational monitoring (both undertaken on a routine basis); and investigative monitoring (carried out where the reason of any exceedance for ecological and chemical status is unknown). Until now, nothing has been developed in relation to investigative monitoring and no clear guidance exists for this type of monitoring, as it must be tackled on a 'case-by-case' basis. Consequently, the present study uses slag disposal from a blast furnace, into a coastal area, as a case-study in the implementation of investigative monitoring, according to the WFD. In order to investigate the potential threat of such slags, this contribution includes: a geophysical study, to determine the extent of the disposal area; sediment analysis; a chemical metal analysis; and an ecotoxicological study (including a Microtox test and an amphipod bioassay). The results show that metal concentrations are several times above the background concentration. However, only one of the stations showed toxicity after acute toxicological tests, with the benthic communities being in a good status. The approaches used here show that contaminants are not bioavailable and that no management actions are required with the slags.