Identification of Gastrointestinal Microbiota in Hawaiian Green Turtles (Chelonia mydas).

Green turtles (Chelonia mydas) have a hindgut fermentation digestive tract, which uses cellulolytic microbes to break down plant matter in the cecum and proximal colon. Previous studies on bacterial communities of green turtles have not identified in situ hindgut microbiota, and never before in Hawaiian green turtles, which comprise an isolated metapopulation. Fresh samples using sterile swabs were taken from five locations along the gastrointestinal tracts of eight green turtles that had required euthanization. Bacteria were cultured, aerobically and anaerobically, on nutrient agar and four differential and selective media. Samples at three sections along the gastrointestinal tracts of two green turtles were analyzed using 16S metagenomics on an Ion Torrent Personal Genome Machine. More than half of the 4 532 104 sequences belonged to the phylum Firmicutes, followed by Bacteroidetes and Proteobacteria, which are characteristic of herbivore gut microbiota. Some microbiota variation existed between turtles and among gastrointestinal sections. The 16S sequence analysis provided a better representation of the total gastrointestinal bacterial community, much of which cannot be cultured using traditional microbial techniques. These metagenomic analyses serve as a foundation for a better understanding of the microbiome of green turtles in the Hawaiian Islands and elsewhere.

Effects of glyphosate herbicide on the gastrointestinal microflora of Hawaiian green turtles (Chelonia mydas) Linnaeus.

In Hawaii, glyphosate-based herbicides frequently sprayed near shorelines may be affecting non-target marine species. Glyphosate inhibits aromatic amino acid biosynthesis (shikimate pathway), and is toxic to beneficial gut bacteria in cattle and chickens. Effects of glyphosate on gut bacteria in marine herbivorous turtles were assessed in vitro. When cultures of mixed bacterial communities from gastrointestinal tracts of freshly euthanized green turtles (Chelonia mydas), were exposed for 24h to six glyphosate concentrations (plus deionized water control), bacterial density was significantly lower at glyphosate concentrations≥2.2×10-4gL-1 (absorbance measured at 600nm wavelength). Using a modified Kirby-Bauer disk diffusion assay, the growth of four bacterial isolates (Pantoea, Proteus, Shigella, and Staphylococcus) was significantly inhibited by glyphosate concentrations≥1.76×10-3gL-1. Reduced growth or lower survival of gut bacteria in green turtles exposed to glyphosate could have adverse effects on turtle digestion and overall health.

Differences in ecological structure, function, and native species abundance between native and invaded Hawaiian streams.

Poeciliids, one of the most invasive species worldwide, are found on almost every continent and have been identified as an "invasive species of concern" in the United States, New Zealand, and Australia. Despite their global prevalence, few studies have quantified their impacts on tropical stream ecosystem structure, function, and biodiversity. Utilizing Hawaiian streams as model ecosystems, we documented how ecological structure, function, and native species abundance differed between poeciliid-free and poeciliid-invaded tropical streams. Stream nutrient yields, benthic biofilm biomass, densities of macroinvertebrates and fish, and community structures of benthic algae, macroinvertebrates, and fish were compared between streams with and without established poeciliid populations on the island of Hawai'i, Hawaii, USA. Sum nitrate (sigmaNO3(-) = NO3(-) + NO2(-)), total nitrogen, and total organic carbon yields were eight times, six times, and five times higher, respectively, in poeciliid streams than in poeciliid-free streams. Benthic biofilm ash-free dry mass was 1.5x higher in poeciliid streams than in poeciliid-free streams. Percentage contributions of chironomids and hydroptilid caddisflies to macroinvertebrate densities were lower in poeciliid streams compared to poeciliid-free streams, while percentage contributions of Cheumatopsyche analis caddisflies, Dugesia sp. flatworms, and oligochaetes were higher. Additionally, mean densities of native gobies were two times lower in poeciliid streams than in poeciliid-free ones, with poeciliid densities being approximately eight times higher than native fish densities. Our results, coupled with the wide distribution of invasive poeciliids across Hawaii and elsewhere in the tropics, suggest that poeciliids may negatively impact the ecosystem structure, function, and native species abundance of tropical streams they invade. This underscores the need for increased public awareness to prevent future introductions and for developing and implementing effective eradication and restoration strategies.

Tracking the sources and sinks of local marine debris in Hawai'i.

Plastic pollution has biological, chemical, and physical effects on marine environments and economic effects on coastal communities. These effects are acute on southeastern Hawai'i Island, where volunteers remove 16 metric tons of debris annually from a 15 km coastline. Although the majority is foreign-origin, a portion is locally-generated. We used floating debris-retention booms in two urban waterways to measure the input of debris from Hilo, the island's largest community, and released wooden drifters in nearby coastal waters to track the fate of that debris. In 205 days, 30 kilograms of debris (73.6% plastic) were retained from two watersheds comprising 10.2% of Hilo's developed land area. Of 851 wooden drifters released offshore of Hilo in four events, 23.3% were recovered locally, 1.4% at distant locations, and 6.5% on other islands. Comparisons with modeled surface currents and wind were mixed, indicating the importance of nearshore and tidal dynamics not included in the model. This study demonstrated that local pollutants can be retained nearby, contribute to the island's debris-accumulation area, and quickly contaminate other islands.

Antioxidant activity of Hawaiian marine algae.

Marine algae are known to contain a wide variety of bioactive compounds, many of which have commercial applications in pharmaceutical, medical, cosmetic, nutraceutical, food and agricultural industries. Natural antioxidants, found in many algae, are important bioactive compounds that play an important role against various diseases and ageing processes through protection of cells from oxidative damage. In this respect, relatively little is known about the bioactivity of Hawaiian algae that could be a potential natural source of such antioxidants. The total antioxidant activity of organic extracts of 37 algal samples, comprising of 30 species of Hawaiian algae from 27 different genera was determined. The activity was determined by employing the FRAP (Ferric Reducing Antioxidant Power) assays. Of the algae tested, the extract of Turbinaria ornata was found to be the most active. Bioassay-guided fractionation of this extract led to the isolation of a variety of different carotenoids as the active principles. The major bioactive antioxidant compound was identified as the carotenoid fucoxanthin. These results show, for the first time, that numerous Hawaiian algae exhibit significant antioxidant activity, a property that could lead to their application in one of many useful healthcare or related products as well as in chemoprevention of a variety of diseases including cancer.

Small plastic debris changes water movement and heat transfer through beach sediments.

We investigated the physical properties of beaches contaminated with plastic fragments. We compared sediment cores from Hawai'i Island's Kamilo Beach, notable for plastic accumulation, to cores from a nearby beach. Compared to the nearby beach, Kamilo sediments contained more plastics (up to 30.2% by weight), were coarser-grained, and were more permeable (t-test, p<0.0001). 85% of the fragments were polyethylene, and 95% were concentrated in the top 15 cm of the cores. We constructed artificial cores of standardized grain size and varying plastic-to-sediment ratios. Adding plastic significantly increased the permeability (ANOVA, p=0.002), which was partially attributed to the fragments increasing the mean grain size. Sediments with plastic warmed more slowly (16% maximum decrease in thermal diffusivity), and reached lower maximum temperatures (21% maximum increase in heat capacity). These changes have a variety of potential effects on beach organisms, including those with temperature-dependent sex-determination such as sea turtle eggs.

Quantitative analysis of small-plastic debris on beaches in the Hawaiian Archipelago.

Small-plastic beach debris from nine coastal locations throughout the Hawaiian Archipelago was analyzed. At each beach, replicate 20 l samples of sediment were collected, sieved for debris between 1 and 15 mm in size, sorted by type, counted and weighed. Small-plastic debris occurred on all of the beaches, but the greatest quantity was found at three of the most remote beaches on Midway Atoll and Moloka'i. Of the debris analyzed, 72% by weight was plastic. A total of 19100 pieces of plastic were collected from the nine beaches, 11% of which was pre-production plastic pellets. This study documents for the first time the presence of small-plastic debris on Hawaiian beaches and corroborates estimates of the abundance of plastics in the marine environment in the North Pacific.