The accumulation of debris is an insidious problem throughout the world’s oceans. Here we document 234.24 items of macro-debris/km² in the shallow populated parts of Majuro lagoon (Republic of the Marshall Islands) which is the second highest standing stock of macro-debris recorded to date in any benthic marine habitat in the world. The majority of macro-debris was from household sources (78.7%) with the peak abundance recorded in areas of medium affluence. Marine debris causes suffocation, shading, tissue abrasion and mortality of corals and we show a significant negative correlation exists between the level of hard coral cover and coverage of marine debris. Given long decomposition times, even if the input of rubbish to Majuro lagoon is stopped immediately, the standing stock of debris will persist for centuries. Multiple new initiatives are needed to curtail the direct and indirect dumping of waste in Majuro lagoon.

Benthic biofilters were deployed under a cage fish farm and in two reference locations to assess the influence of the farm on the biofilters and the surroundings, as well as to verify the usefulness of this technology as a mitigation tool. The biofilters underneath the farm recruited a fouling community practically identical to that of the control biofilters, which included a variety of trophic strategies. The former showed a higher ¹⁵N enrichment, indicating that fouling beneath the farm was benefiting from the farm waste. The waste retention efficiency was low (0.02gNm⁻²month⁻¹) beneath the farm. Benthic biofilters aggregated demersal wild fish around and within them. Pelagic wild fish also frequently used the biofilters beneath the farm, forming compact shoals around them. The increased complexity of the habitat below the fish farm enhanced biodiversity, but this improvement did not lead to the recovery of the sediments around the biofilters.

Environmental pollution due to heavy metals is having an increased impact on marine wildlife accentuated by anthropogenic changes in the planet including overfishing, agricultural runoff and marine emerging infectious diseases. Sea turtles are considered sentinels of ecological health in marine ecosystems. The objective of this study was to determine baseline concentrations of zinc, cadmium, copper, nickel, selenium, manganese, mercury and lead in blood of 22 clinically healthy, loggerhead turtles (Caretta caretta), captured for several reasons in Puerto López Mateos, Baja California Sur, Mexico. Zinc was the most prevalent metal in blood (41.89μgg⁻¹), followed by Selenium (10.92μgg⁻¹). The mean concentration of toxic metal Cadmium was 6.12μgg⁻¹ and 1.01μgg⁻¹ respectively. Mean concentrations of metals followed this pattern: Zn>Se>Ni>Cu>Mn>Cd>Pb and Hg. We can conclude that blood is an excellent tissue to measure in relatively non-invasive way baseline values of heavy metals in Caretta caretta.

The concentrations of heavy metals and organic carbon in sediment of the Homa Lagoon which is one of the most productive lagoons and commercial important active fish trap in the Eastern Aegean Sea, were investigated in order to describe the temporal and spatial distributions of metals. These results were used to evaluate possible ecological risks that could be a problem for the environment of the lagoon in the future. Sediments were enriched with Cr, Ni and considered as heavily polluted per the SQG. The Cf of Ni and Cr were presented moderate level of contamination in this area. The Cd levels indicated moderate degree of contamination at station B, C, D and E due to agricultural drainage water, industrial and domestic wastewater, are transported by the Gediz River. Sediments from Homa Lagoon were most toxic for Ni due to exceedances of the TEL and PEL values.

We examined the occurrence of marine debris in the gastrointestinal tract of 54 loggerhead sea turtles (Caretta caretta) found stranded or incidentally captured dead by fisheries in the Adriatic Sea, with a curved carapace length of 25.0–79.2cm. Marine debris was present in 35.2% of turtles and included soft plastic, ropes, Styrofoam and monofilament lines found in 68.4%, 42.1%, 15.8% and 5.3% of loggerheads that have ingested debris, respectively. The dry mass of debris per turtle was low, ranging from <0.01 to 0.71g, and the ingestion was not significantly affected by sex or body size (all p>0.05). Marine debris averaged 2.2±8.0% of dry mass of gut content, with a maximum of 35% found in a juvenile turtle that most likely died due to debris ingestion. Considering the relatively high occurrence of debris intake and possible sub-lethal effects of even small quantities of marine debris, this can be an additional factor of concern for loggerheads in the Adriatic Sea.

Mercury concentrations were assessed in the sea turtle Lepidochelys olivacea from a nesting colony of Oaxaca, Mexico; 25 female turtles were sampled, a total of 250 eggs were collected during the season 2005–2006. Higher concentrations were found in yolk fraction, while in blood and albumen mean levels were below of 0.0010μgg⁻¹ dry wt. On the basis of one nesting season, the maternal transfer of Hg via eggs-laying was estimated in 2.0±1.1%. According to international norms, the health of this population and its habitats is acceptable for Hg and corresponds to baseline levels of a nearly pristine environment.

We reconstructed the first long-term (∼400years) records of black carbon (BC) deposition flux from three ornithogenic sediment profiles, which were collected from three remote, isolated islets of the Xisha archipelago, South China Sea. The significant correlations between black carbon, organic matter and excess ²¹⁰Pb suggested that black carbon was mainly derived from atmospheric deposition, and further enriched by plant-derived organic matter in sediments. During the past 400years, the BC flux remained relatively low before the onset of 20th century; it started to increase from approximately 1900 AD, and peaked around the 1970s. In the recent 30years, the BC flux seemed to display decreasing trend, very likely due to the change of energy structure and development of pollution control techniques. In comparison with marginal sea regions that are greatly impacted by anthropogenic activities, these pristine Xisha islands were not significantly influenced by black carbon of anthropogenic origin.

The increasing use of nanotechnology highlights the need to understand and clarify the environmental impacts of nanomaterials. In this study, the acute toxicity and oxidative stress of titanium dioxide nanoparticles (nTiO₂) in mature marine abalone (Haliotis diversicolor supertexta) were assessed. No acute effect was found in any of the treatment groups with nTiO₂ concentration gradients ranging from 0.1 to 10mg/L. However, the activity of an antioxidant enzyme superoxide dismutase (SOD) significantly increased in the group that was exposed to 1.0mg/L nTiO₂. The content of a non-enzymatic antioxidant, glutathione (GSH), significantly decreased in the groups with an nTiO₂ concentration ⩾1.0mg/L. The level of lipid peroxidation (LPO) was found to increase as the nTiO₂ dose increased. Furthermore, NO was produced in excess in abalone. These results demonstrated that, although nTiO₂ is not acutely toxic to abalone, it does exert oxidative stress on abalone.

Iron (Fe) plaque formed on mangrove root increased with wastewater discharge, but the extent was species-specific. For Bruguiera gymnorrhiza, Fe plaque concentration was 0.80mgg⁻¹ root d.wt at Day 0 and increased to 4.59, 6.84 and 7.52mgg⁻¹ at Day 75 in the fresh water control (FW), synthetic wastewater with pollutant concentrations five times of municipal sewage (5SW) and double of 5SW (10SW) treatments, respectively; the respective increases in Excoecaria agallocha were from 0.70 to 2.37, 10.73 and 13.21mgg⁻¹. For Acanthus ilicifolius, similar increase was found in 5SW, but all of the plants were dead in 10SW at Day 75. The concentrations of heavy metals and phosphorus immobilized were positively correlated with the amounts of Fe plaque formed, but the regression coefficients varied among species. The performance of mangrove plants in wastewater treatments was related to the Fe plaque formed and its immobilized wastewater-borne pollutants.

The bacterial communities in the anoxic layer of a heavily polluted microbial mat and their growth on hydrocarbons under sulfate-reducing conditions were investigated. Microbial communities were dominated by members of Alphaproteobacteria (27% of the total rRNA), Planctomycetes (21.1%) and sulfate-reducing bacteria (SRB: 17.5%). 16S rRNA cloning revealed sequences beloning to the same bacterial groups with SRB affiliated to the genera Desulfobulbus, Desulfocapsa, Desulfomicrobium, Desulfobacterium and Desulfosarcina/Desulfococcus. The derived enrichment cultures on crude oil, hexadecane and toluene were dominated by SRB. While most SRB sequences of the toluene and hexadecane cultures were related to the sequence of Desulfotignum toluolica, the crude oil enrichment showed a more diverse bacterial community with sequences from the genera Desulfotignum, Desulfobacter, Desulfatibacillus, Desulfosalina, and Desulfococcus. We conclude that the anoxic layer of the studied mats contains a diverse community of anaerobic bacteria, dominated by SRB, some of which are able to grow on hydrocarbons.