Potentially toxic elements (PTEs) are of major concern due to their high persistence and toxicity. Recently, rare earth elements (REEs) concentration in aquatic ecosystems has been increasing due to their application in modern technologies. Thus, this work aimed to study, for the first time, the influence of REEs (lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, dysprosium and yttrium) and of salinity (10 and 30) on the removal of PTEs (Cd, Cr, Cu, Hg, Ni and Pb) from contaminated waters by living macroalgae (Fucus spiralis, Fucus vesiculosus, Gracilaria sp., Osmundea pinnatifida, Ulva intestinalis and Ulva lactuca). Experiments ran for 168 h, with each macroalga exposed to saline water spiked with the six PTEs and with the six PTEs plus nine REEs (all at 1 μmol L⁻¹) at both salinities. Results showed that all species have high affinity with Hg (90–99% of removal), not being affected neither by salinity changes nor by the presence of other PTEs or REEs. Cd showed the lowest affinity to most macroalgae, with residual concentrations in water varying between 50 and 108 μg L⁻¹, while Pb removal always increased with salinity decline (up to 80% at salinity 10). REEs influence was clearer at salinity 30, and mainly for Pb. No substantial changes were observed in Ni and Hg sorption. For the remaining elements, the effect of REEs varied among algae species. Overall, the results highlight the role of marine macroalgae as living biofilters (particularly U. lactuca), capable of lowering the levels of top priority hazardous substances (particularly Hg) and other PTEs in water, even in the presence of the new emerging contaminants - REEs. Differences in removal efficiency between elements and macroalgae are explained by the contaminant chemistry in water and by macroalgae characteristics.

One of the objectives of the BALMAS project was to conduct Port Baseline Biological Surveys of native and non-indigenous benthic flora in 12 Adriatic ports. Samples of macroalgae growing on vertical artificial substrates were collected in spring and autumn 2014 and/or 2015. A total number of 248 taxa, 152 Rhodophyta, 62 Chlorophyta, and 34 Ochrophyta, were identified. Of these, 13 were non-indigenous seaweeds, mainly filamentous macroalgae, that were probably introduced through hull fouling. Some of these taxa had already been described in the study areas, others were recorded for the first time, a few were no longer detected at sites where they had previously been recorded (e.g. Sargassum muticum). Some other NISS reported for the Adriatic Sea, were not collected at any sampling site (i.e. Caulerpa cylindracea, Codium fragile). Possible reasons for the absence of these species are discussed.

δ15N of annual (Ulva sp., Porphyra sp.) and perennial intertidal seaweed species (Chondrus crispus, Fucus sp.) collected on 17 sampling points along the French coast of the English Channel in 2012 and 2013 were assessed on their suitability as bioindicators of N pollution in coastal areas. A sine function applied for δ15N time series data showed for all the species the same seasonal trend with lowest δ15N values in April and highest in summer but with no significant interspecific differences of amplitude (α) and phase angle (ϕ). This model provides a useful tool for monitoring the inter-annual changes of N pollution. An interspecific variability of δ15N values was observed, probably due to their tolerance to emersion. An in vitro study for comparing the kinetic acquisition of the isotopic signal and N uptake mechanisms of each species underlined the influence of algal physiology on the δ15N interspecific variability.

The Cystoseira ericaefolia group is conformed by three species: C. tamariscifolia, C. mediterranea and C. amentacea. These species are among the most important habitat forming species of the upper sublittoral rocky shores of the Mediterranean Sea and adjacent Atlantic coast. This species group is sensitive to human pressures and therefore is currently suffering important losses. This study aimed to assess the influence of anthropogenic pressures, oceanographic conditions and local spatial variability in assemblages dominated by C. ericaefolia in the Alboran Sea. The results showed the absence of significant effects of anthropogenic pressures or its interactions with environmental conditions in the Cystoseira assemblages. This fact was attributed to the high spatial variability, which is most probably masking the impact of anthropogenic pressures. The results also showed that most of the variability occurred on at local levels. A relevant spatial variability was observed at regional level, suggesting a key role of oceanographic features in these assemblages.

Bioaccumulation of organochlorine pesticides (OCPs) in red, green, and brown seaweeds from the Gulf of Mannar was investigated using gas chromatography–mass spectrometry (GC–MS). The concentration of OCPs in all the seaweeds was in the order of endosulfan > endrin > HCH > DDT > aldrin > heptachlor > methoxychlor. The concentrations of HCH, endrin, endosulfan, and DDT in Sargassum wightii and Gelidiella acerosa, and HCH and endosulfan in Gracilaria verrucosa were above the limits prescribed by the European Commission. However, in Ulva lactuca, except for endosulfan, all other OCPs were below the permissible level. The bioaccumulation of OCPs in seaweeds was in the order of S. wightii > G. acerosa > Gracilaria verrucosa > U. lactuca. The results of comparative analysis of the levels of the investigated pesticides against the standard human health risk assessment revealed that pesticide exposure from seaweeds is hazardous to human health and the marine environment of the Gulf of Mannar.

It has been predicted that Grateloupia turuturu, native of the cold-temperate waters of Japan, is one of the most invasive marine species considered as a threat to global marine biodiversity. However, few studies have been carried out to assess the extent of its spread worldwide. Its seasonal dynamics in the Mar Piccolo of Taranto, a transitional water system in the Northern Ionian Sea, were observed for ten years. Systematic monthly observations were carried out from 2008 to 2018. The length of thalli and density were measured alongside the seawater temperature. Data were processed by means of non-parametric statistical analyses. No invasive behavior was detected for G. turuturu. It seems well established in the Mar Piccolo even though its population is limited to the station of first detection. However, due to its shown preference for plastic substrate, it could become a vector of another urgent threat, that is plastic pollution.

Besides being food and a refuge to marine species, macroalgae are a powerful and renewable economic resource. However, they may introduce microplastics (MPs) in the trophic chain. We developed a reliable analytical method to characterize and quantify MPs in common and edible macroalgae. Several digestion methods and filters, along with various measurement options, were studied. A new enzymatic-oxidative protocol with a unique final filtration was selected and validated with a mixture of 5 commercial macroalgae (Undaria pinnatifida spp, Porphyra spp, Ulva spp, Laminaria ochroleuca and Himanthalia elongate). Further, it was shown that washing the macroalgae to release MPs is suboptimal and the potential adhesion of MPs to macroalgae was evaluated. A filter subsampling strategy that scans 33.64 % of its surface reduced the time required to characterize <70 μm particles and fibres directly on the 47 mm diameter filter using an IR microscope (1 sample/day).

Intensive mariculture results in a rise in nutrient concentrations, then leads to serious eutrophication in coastal waters. Based on the sampling data obtained between August 2012 and July 2013, the eutrophication status in Yantian Bay was assessed, and the proportion of marine animals co-cultured with seaweeds was evaluated. The nutritional quality index (NQI) ranged from 4.37 to 13.20, indicating serious eutrophication conditions. The annual average ratio of nitrogen/phosphorus (N/P) was 25.19, indicating a nitrogen surplus in this system. DIN was selected as the best parameter to balance seaweed absorption and marine animal DIN production. Gracilaria lemaneiformis and Laminaria japonica were selected as co-cultured seaweeds. The optimal proportion of G. lemaneiformis production was assessed as 20074.14 tonnes. The optimal proportion of L. japonica production was evaluated as 15890.68 tonnes. High-temperature adapted seaweeds should be introduced for removing nutrients releasing by farmed aquatic animals in the summer in Yantian Bay.

In this study, the bioremediation potentials of two seaweeds (Sargassum hemiphyllum and S. henslowianum) against pollution in a coastal mariculture area of Shenzhen, South China, were investigated by comparing the growth, nutrient bioaccumulation capacity of plants from the seaweed bed (control site) with plants from the fish farm. Results indicated that both species are potential candidates for bioremediation in the fish farm areas in terms of their high growth rates and high bioaccumulation capacities on inorganic nutrients. Both Sargassum spp. contain high levels of crude protein (11.7–14.0%) and crude fat (2.2–2.7%), suggesting high nutritional values. The S. hemiphyllum may serve as a good aquaculture fodder with high nutritional compositions and low heavy metal contents. However, heavy metals (Cr, Pb and Cd) of S. henslowianum exceed the maximum allowable concentrations as aquatic feed, which restricts its fodder application. In general, the results of this study may contribute to the marine pollution bioremediation in the coastal areas of South China, especially in mariculture zones.

The release of textile effluents into the biosphere is a serious threat to the environment and promotes several health issues. Although several studies have been carried out in the remediation of textile effluents using adsorbents, the continuous mode of operation (packed bed) to treat effluent generated from the cotton-based textile industry using biosorbent is seldom reported. Here, one such investigation is made to remediate the Remazol effluent solution in batch and continuous mode of operation. A maximum decolourization efficiency of 77.5% and 49.66% was obtained for Ulva lactuca derived biochar in batch and continuous study. Column data parameters such as overall sorption time zone, breakthrough time, exhaustion time and volume of effluent treated were also calculated. Regeneration studies showed that 0.01 M sodium hydroxide can be utilized for sorption-elution up to three regeneration cycles.