Occurrence of microplastics within a freshwater aquaculture system in the Pacific Islands, Viti Levu, Fiji.

Microplastics (MPs) have become frequent topics of research within Pacific Islands (PIs) in recent years; however, within PI freshwater aquaculture systems, MPs have not yet been quantified. As such this study is aimed at quantifying and characterizing the MP load from across a freshwater aquaculture system within Fiji. Water, sediment, and fish samples were collected from various stages between water source and drainage channels of an aquaculture facility in Navua, Fiji. MPs were extracted using established protocols and analyzed for abundance, form type, size, and polymer composition. Results show no significant difference in MP abundance between sampling sites for, water (average: 3.2 ± 1.14 MP/L), sediment (average: 2.3 ± 0.7 MP/100 g DW), and fish (average: 2.7 ± 1.4 MP/fish). Fibers were the most frequent form type in all three elements (average: 2.9 ± 0.2 MP/L in water, 2.1 ± 0.75 MP/100 g DW, 2.8 ± 0.14 MP/fish); however, the difference across sites was significant within water samples only. In water and sediments, smaller MPs (< 1.4 mm) were the most frequent comprising > 35% in all three elements; however, the difference was not significant between sites. Polymer analysis found that polypropylene, polyurethane, and nylon were the most abundant polymers, which coupled with observed form type and size characteristics suggest a common sources of MPs across sites.

Redirection of ambient light improves predator detection in a diurnal fish.

Cases where animals use controlled illumination to improve vision are rare and thus far limited to chemiluminescence, which only functions in darkness. This constraint was recently relaxed by studies on Tripterygion delaisi, a small triplefin that redirects sunlight instead. By reflecting light sideways with its iris, it has been suggested to induce and detect eyeshine in nearby micro-prey. Here, we test whether 'diurnal active photolocation' also improves T. delaisi's ability to detect the cryptobenthic sit-and-wait predator Scorpaena porcus, a scorpionfish with strong daytime retroreflective eyeshine. Three independent experiments revealed that triplefins in which light redirection was artificially suppressed approached scorpionfish significantly closer than two control treatments before moving away to a safer distance. Visual modelling confirmed that ocular light redirection by a triplefin is sufficiently strong to generate a luminance increase in scorpionfish eyeshine that can be perceived by the triplefin over 6-8 cm under average conditions. These distances coincide well with the closest approaches observed. We conclude that light redirection by small, diurnal fish significantly contributes to their ability to visually detect cryptic predators, strongly widening the conditions under which active sensing with light is feasible. We discuss the consequences for fish eye evolution.

Screening of pharmaceuticals in coastal waters of the southern coast of Viti Levu in Fiji, South Pacific.

The global reliance on pharmaceuticals coupled with the lack of effective treatment methods has resulted in pseudo-persistence of pharmaceuticals within the environment. Globally, efforts to quantify and monitor pharmaceuticals within the environment have been well underway, however few studies have been made within small Pacific Islands. This study aims at screening for the occurrence and concentration of pharmaceutical residues within the southern coastal waters of Fiji's main island, Viti Levu. Water samples were collected from a depth of ca. 0.6 m from seven sites and were analyzed for 80 pharmaceuticals via a combination of chromatography and heated electrospray ionization. Seventy-two pharmaceuticals were quantified at least once with average concentrations ranging between 0.04 ng/L (diltiazem) and 19 ng/L (ketoconazole), and with all but two pharmaceuticals (trimethoprim and biperiden) being present in less than 50% of the samples. Findings suggest that even though the release of pharmaceuticals into the marine environment is sporadic and pharmaceuticals are diluted via turbulent mixing, there are measurable concentrations of pharmaceuticals in Fiji and these pollutants are not necessarily restricted to highly populated areas.

Microplastics in subsurface coastal waters along the southern coast of Viti Levu in Fiji, South Pacific.

Microplastics (MPs) remain largely understudied in Small Island Developing States. This study is aimed at comparing the abundance and characteristics of MPs in rural and urban marine coastal sites located along the southern coast of Fiji's main inhabited island, Viti Levu. Collection of subsurface waters (at depth of ca. 0.6 m) was performed at seven sites via Niskin bottle. Samples were filtered over a membrane filter to extract MPs and to allow visual analysis and polymer identification by using attenuated total reflectance in Fourier transform infrared spectroscopy. Findings from this study depict widespread presence of MPs in both urban and rural sites, and show no significant differences in the four parameters studied, i.e. abundance of MP pieces (2.0 vs 1.6 MP/L, respectively), form types (dominance of fibers), size (0.5-0.9 and 1.0-1.4 mm totaling 48% of the samples), and color (blue contributing 30%, and red and black contributing 25% each). These findings challenge the common expectation of a higher MPs pollution in urban areas compared to rural areas.