Ph.D. Hinojosa-Toledo, Ivan

Anthropogenic Marine Debris (AMD) in the SE Pacific has primarily local origins from land-based sources, including cities (coastal and inland), beach-goers, aquaculture, and fisheries. The low frequency of AMD colonized by oceanic biota (bryozoans, lepadid barnacles) suggests that most litter items from coastal waters of the Humboldt Current System (HCS) are pulled offshore into the South Pacific Subtropical Gyre (SPSG). The highest densities of floating micro- and macroplastics are reported from the SPSG. An extensive survey of photographic records, unpublished data, conference proceedings, and published studies revealed interactions with plastics for 97 species in the SE Pacific, including 20 species of fish, 5 sea turtles, 53 seabirds, and 19 marine mammals. Sea turtles are most affected by interactions with plastics, underlined by the fact that 4 of the 5 species suffer both from entanglement and ingestion. Reports gathered in this review suggest that interactions along the continental coast are mostly via entanglement. High frequencies of microplastic ingestion have been reported from planktivorous fish and seabirds inhabiting the oceanic waters and islands exposed to high densities of microplastics concentrated by oceanic currents in the SPSG. Our review also suggests that some species from the highly productive HCS face the risk of negative interactions with AMD, because food and plastic litter are concentrated in coastal front systems. In order to improve the conservation of marine vertebrates, especially of sea turtles, urgent measures of plastic reduction are needed.

Consumer pressure in benthic communities is predicted to be higher at low than at high latitudes, but support for this pattern has been ambiguous, especially for herbivory. To understand large-scale variation in biotic interactions, we quantify consumption (predation and herbivory) along 2500 km of the Chilean coast (19°S–42°S). We deployed tethering assays at ten sites with three diferent baits: the crab Petrolisthes laevigatus as living prey for predators, dried squid as dead prey for predators/scavengers, and the kelp Lessonia spp. for herbivores. Underwater videos were used to characterize the consumer community and identify those species consuming baits. The species composition of consumers, frequency of occurrence, and maximum abundance (MaxN) of crustaceans and the blenniid fsh Scartichthys spp. varied across sites. Consumption of P. laevigatus and kelp did not vary with latitude, while squid baits were consumed more quickly at mid and high latitudes. This is likely explained by the increased occurrence of predatory crabs, which was positively correlated with consumption of squidpops after 2 h. Crabs, rather than fsh, were the principal consumers of squid baits (91% of all recorded predation events) at sites south of 30°S. Fish and crustaceans preyed in similar proportion on P. laevigatus, with most fsh predation events at northern sites. The absence of any strong latitudinal patterns in consumption rate of tethered prey is likely due to redundancy among consumers across the latitudinal range, with crustaceans gaining in importance with increasing latitude, possibly replacing fsh as key predators.