Monitoring the abundance and characteristics of microplastics in estuarine waters is crucial for understanding the fate of microplastics at the land-sea continuum, and for developing policies and legislation to mitigate associated risks. However, if protocols to monitor microplastic pollution in ocean waters or beach sediments are well established, they may not be adequate for estuarine environments, due to the complex 3D hydrodynamics. In this note, we review and discuss sampling methods and strategies in relation to the main environmental forcing, estuarine hydrodynamics, and their spatio-temporal scales of variability. We propose recommendations about when, where and how to sample microplastics to capture the most representative picture of microplastic pollution. This note opens discussions on the urgent need for standardized methods and protocols to routinely monitor microplastics in estuaries which should, at the same time, be easily adaptable to the different systems to ensure consistency and comparability of data across different studies.

Distribution and behavior of many trace elements in the aquatic environment has been well characterized, but little is known about silver (Ag) concentrations in coastal waters, even though this element ranks among the most toxic to marine invertebrates (Calabrese et al., 1977 ; Fisher and Hook, 1997 ; Webb and Wood, 1998). Studies conducted by Flegal et al. (1995), River-Duarte et al. (1999), and Ndung'u et al. (2001), provided the first valuable data on Ag distribution in the oceanic environment, indicating that this element is found in very low concentrations in the dissolved phase. However, although silver concentrations in coastal waters do not reach the nanomolar range (Smith and Flegal, 1993 ; Squire et al., 2002), formation of a stable chloro complex enhances bioavailability and toxicity to biota (Luoma et al., 1995). Experimental studies have shown that Ag is toxic to some living organisms at environmentally realistic levels (Bryan and Langston, 1992). Silver found in the aquatic environment mainly originates in effluents from sewage treatment plants (Rozan and Hunter, 2001). Silver can therefore be used as a tracer of wastewater discharges in coastal waters (Martin et al., 1988 ; Sañudo-Wilhelmy and Flegal, 1992), for instance through the use of sentinel organisms, which concentrate bioavailable contaminants in their tissues (Stephenson and Leonard, 1994 ; Jiann and Presley, 1997 ; Riedel et al., 1998 ; Muñoz-Barbosa et al., 2000). This study concerns biological monitoring as a means of providing a synoptic view of silver contamination in French coastal waters. The National Network for the Observation of Marine Environment Quality (RNO, the French Mussel-Watch) which has been regularly measuring concentrations of various chemical contaminants in oyster and mussel tissues for 25 years (Claisse, 1989), has been monitoring silver levels since 2003. This valuable database including data collected at 80 sampling sites distributed along the French coasts (Fig. 1), is used as a reference to provide the spatial distribution of a given contaminant (Chiffoleau and Bonneau, 1994), identify trends of contamination/decontamination (Chiffoleau et al., 2001), and detect peak concentrations due to accidental events (Chiffoleau et al., 2004). Mussels (Mytilus edulis and Mytilus galloprovincialis) and oysters (Crassostrea gigas) are collected twice a year in February and November. Sample collection (size of samples, size of animals) and treatment (cleaning, depuration, removal of soft parts from the shells, draining, homogenization, and freeze-drying) are performed according to the OSPAR Convention guidelines and the method described by Claisse (1989).

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify Cs-137 levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While: measured Cs-137 levels were found to be very low (usually <1 Bq kg(-1) wet wt) Cs-137 activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area. (C) 2007 Elsevier Ltd. All rights reserved.

The work presented here aims at comparing monitoring of S-metolachlor, the major pesticide in use in the Arcachon Bay (South West of France, transitional coastal area), by chemical analysis (monthly passive sampling) and contaminant dissipation modeling from sources (Mars-2D model). The global strategy consisted in i) identifying the major sources of S-metolachlor to the Bay, ii) monitoring these sources for 12 months, and iii) comparing modeled data in the Bay based on measured inputs, to chemical measurements made inside the Bay along with the 12-month source monitoring. Results first showed that the major S-metolachlor surface inputs to the Arcachon Bay are mainly from one single source. Modeled and measured data were in good agreement at 5 sites in the Bay, both in terms of concentration range and seasonal trends. Modeling thus offers a cost-effective solution for monitoring contaminants in transitional waters, overcoming in addition the technical limitations for measuring pg L−1 or lower levels in coastal waters. However, we highlighted that secondary sources may affect accuracy at local level.

Adverse effects of invasive alien species (IAS), or biological pollution, is an increasing problem in marine coastal waters, which remains high on the environmental management agenda. All maritime countries need to assess the size of this problem and consider effective mechanisms to prevent introductions, and if necessary and where possible to monitor, contain, control or eradicate the introduced impacting organisms. Despite this, and in contrast to more enclosed water bodies, the openness of marine systems indicates that once species are in an area then eradication is usually impossible. Most institutions in countries are aware of the problem and have sufficient governance in place for management. However, there is still a general lack of commitment and concerted action plans are needed to address this problem. This paper provides recommendations resulting from an international workshop based upon a large amount of experience relating to the assessment and control of biopollution. Highlights ► We summarize the results of an international workshop on marine biopollution. ► We recommend science-based information support for bioinvasion management. ► We outline types of bioinvasion monitoring and consider topical research needs. ► We emphasize the role of taxonomy training and public involvement. ► Biopollution should be treated in the same way as any other type of pollution.

Plasticizers are compounds often involved in the manufacturing of plastic products. Nevertheless, the ageing of the latter generates plasticizers that generally end up in the marine environment. In fact, marine pollution by phthalate acid esters (PAEs) and their alternatives has become an environmental and health issue of serious concern, as they are largely and ubiquitously present in the environment and aquatic organisms. In the present study, four PAEs, such as diethyl phthalate (DEP), diisobutyl phthalate (DiBP), dibutyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP), and one non-phthalate plasticizer (NPP), namely di-2-ethylhexyl terephthalate (DEHT), are wanted in different marine compartments from the coast of Mahdia in Tunisia such as sediment, seagrass, and mussel. The most abundant and frequently detected congener was DEHT at the concentrations reached 1.181 mg/kg in the sediment, 1.121 mg/kg in the seagrass, and 1.86 mg/kg in the mussel. This result indicates that the DEHT could emerge through the food chain and therefore bioaccumulate in marine compartments. In addition, we noticed that the seasonal variations of plasticizers were seriously affected by environmental factors including industrial and urban discharges.