Host ecology and biogeography drive parasite community composition in Atlantic killifishes.

Understanding the mechanisms of parasite community assembly can be confounded by phylogenetic distance among host species. Addressing this requires focusing on parasite communities within closely related taxa. Thus, we took a macroecological approach to examining parasite community structure within Killifish species in the genus Fundulus to disentangle the effects of host phylogeny and ecological variables. We constructed a database of parasite communities within Fundulus species from 15 published and unpublished surveys covering the Atlantic coast of the US and Canada. The database was expanded by sampling sites in underrepresented provinces and states, totaling 10 Fundulus species from 57 unique geographic sites. Univariate analysis of observed parasite species richness among Fundulus populations in the dataset found that latitude, climate type, and salinity were the dominant factors determining parasite species richness. Multivariate analysis found that host species and landscape type were the most important factors in determining the similarity of parasite assemblages. Unexpectedly, parasite species richness decreased in low latitudes, and host phylogenetic distance was not found to be a significant factor in the similarity of parasite communities. These results indicate that commonly reported large-scale drivers of parasite community structure, such as latitude and phylogeny, could have diminished significance at the host genus level relative to host ecology, biogeography, and local landscape factors.

Age, growth and maturity of the yellow stingray (Urobatis jamaicensis), a biannually reproductive tropical batoid.

Urobatis jamaicensis is a coastal batoid species affected by habitat loss and small-scale exploitation from fisheries and the aquarium trade, yet the life-history information available is limited. This is the first study to assess the vertebral centra from 195 stingrays to estimate age and growth patterns, and compare them with the biannual reproductive pattern previously reported for this species. Age-at-size data were compared using five different growth models and found a two-parameter von Bertalanffy growth function (VBGF), the Gompertz model and a modified VBGF fit best for males, females and sexes combined, respectively. Maturity was achieved before 1 year. However, growth did not cease with the onset of maturity, but instead slowed down. Results from marginal increment analysis and edge analysis indicated a nonannual somatic growth pattern with influences from the biannual reproduction cycle where peaks in resource allocation may be focused on ovulation rather than growth during March when larger brood sizes are present, while resources may be allocated more towards growth during August and September when brood sizes are generally smaller. These results may be used as a proxy for species with similar reproductive patterns or for those that lack annual or seasonal growth patterns.

Accumulation of the Toxic Metal Mercury in Multiple Tissues of Marine-Associated Birds from South Florida.

One of the best studied global "hot spots" for ecological mercury (Hg) contamination is south Florida (USA), where elevated Hg concentrations in environmental media and regional wildlife were first described over thirty years ago. While Hg contamination has lessened in this region, it is still critical to monitor Hg uptake and potential risks in south Florida wildlife, especially in marine-associated birds, which are known to accumulate potentially toxic Hg levels. In this study, total Hg (THg) concentrations were measured in liver, kidney, muscle, and feathers of 101 individuals from seven species of south Florida birds: brown pelican Pelecanus occidentalis, double-crested cormorant Phalacrocorax auratus, herring gull Larus argentatus, laughing gull Leucophaeus atricilla, northern gannet Morus bassanus, royal tern Thalasseus maximus, and osprey Pandion halietus. A sizeable proportion of individuals (> 40%) were found to contain THg concentrations in internal tissues that exceeded estimated toxicity thresholds for Hg-related effects. Certain species, especially osprey, were found to exhibit a higher rate of threshold exceedances than others and should continue to be monitored for Hg-related effects in future studies. Feather THg concentrations exhibited a lower rate of toxicity threshold exceedances (12%) and were not significantly correlated with those in internal tissues in most cases, suggesting that they may not be well suited for monitoring Hg exposure in these species unless sources of data variation can be better understood. The results of the present study contribute significantly to our understanding of trends in Hg accumulation and Hg-related health risks in south Florida marine-associated birds.

Stable isotopes and community surveys reveal differential use of artificial and natural reefs by South Florida fishes.

Artificial reefs may enhance the biological production of reef-associated flora and fauna, but their trophic structure relative to that of natural reefs remains understudied. We assessed trophic relationships by 1) comparing reef fish communities and 2) comparing δ13C and δ15N in 43 fish species from both artificial reef sites and adjacent natural reef tracts in Broward County, Florida. We tested the effect of sampling location (artificial, first, and second reef), general feeding strategy (herbivore, omnivore, invertivore, and carnivore), phylogeny, and standard length on δ13C and δ15N. The reef fish communities of the artificial and natural reef tracts were significantly different; the artificial sites also exhibited more variability. For all samples, δ13C and δ15N ranged from -19.5 to -13.1‰ and 6.7-13.3‰, respectively. Significant effects were detected for both general feeding strategy and phylogeny. Significant differences were also seen in δ13C and δ15N profiles between artificial and natural reefs; however, these changes were primarily driven by differences in fish community structure, rather than by changes in the feeding strategy or trophic relationships of individual fish taxa. The trophic guild invertivore was the only group of fish to demonstrate significant isotopic differences between both reef tracts (inner and outer) and reef types (artificial and natural). The artificial reef may act more as a foraging corridor between the natural first and second reef tracts for omnivores and carnivores. If the function of artificial reefs is to provide additional foraging habitat for fishes, then perhaps more time is needed for the trophically important, infaunal invertebrate community to develop similarly to the natural reef environment.

Ports and pests: Assessing the threat of aquatic invasive species introduced by maritime shipping activity in Cuba.

Aquatic invasive species (AIS) are biological pollutants that cause detrimental ecological, economic, and human-health effects in their introduced communities. With increasing globalization through maritime trade, ports are vulnerable to AIS exposure via commercial vessels. The Cuban Port of Mariel is poised to become a competitive transshipment hub in the Caribbean and the intent of this study was to evaluate present and potential impacts AIS pose with the likely future increase in shipping activity. We utilized previous assessment frameworks and publicly accessible information to rank AIS by level of threat. Fifteen AIS were identified in Cuba and one, the Asian green mussel Perna viridis (Linnaeus, 1758), had repeated harmful economic impacts. Five species associated with trade partners of Port Mariel were considered potentially detrimental to Cuba if introduced through shipping routes. The results presented herein identify species of concern and emphasize the importance of prioritizing AIS prevention and management within Cuba.

Bioaccumulation and biomagnification of mercury and methylmercury in four sympatric coastal sharks in a protected subtropical lagoon.

Mercury bioaccumulation is frequently observed in marine ecosystems, often with stronger effects at higher trophic levels. We compared total mercury (THg) and methylmercury (MeHg) from muscle with length, comparative isotopic niche, and diet (via δ13C and δ15N) among four sympatric coastal sharks in Florida Bay (USA): blacknose, blacktip, bull, and lemon. Mercury in blacknose and blacktip sharks increased significantly with size, whereas bull and lemon sharks had a high variance in mercury relative to size. Both δ13C and δ15N were consistent with general resource use and trophic position relationships across all species. A significant relationship was observed between δ13C and mercury in blacktip sharks, suggesting an ontogenetic shift isotopic niche, possibly a dietary change. Multiple regression showed that δ13C and δ15N were the strongest factors regarding mercury bioaccumulation in individuals across all species. Additional research is recommended to resolve the mechanisms that determine mercury biomagnification in individual shark species.