Ph.D. Hinojosa-Toledo, Ivan

We examined the hypothesis that in an emerging economy such as Chile the abundances of Anthropogenic Marine Debris (AMD) on beaches are increasing over time. The citizen science program Científicos de la Basura (“Litter Scientists”) conducted three national surveys (2008, 2012 and 2016) to determine AMD composition, abundance, spatial patterns and temporal trends. AMD was found on all beaches along the entire Chilean coast. Highest percentages of AMD in all surveys were plastics and cigarette butts, which can be attributed to local sources (i.e. beach users). The Antofagasta region in northern Chile had the highest abundance of AMD compared with all other zones. Higher abundances of AMD were found at the upper stations from almost all zones. No significant tendency of increasing or decreasing AMD densities was observed during the 8 years covered by our study, which suggests that economic development alone cannot explain temporal trends in AMD densities.

Larval behavior plays an important role in dispersal and settlement of marine organisms with cues from the environment often providing crucial guidance for facilitating these processes. The postlarvae, or pueruli, of the southern rock lobster, Jasus edwardsii (Hutton, 1875), are known to migrate over long distances from oceanic water and settle on coastal reefs using a combination of onshore transport and active nocturnal swimming. In laboratory experiments, we examined environmental cues used for this migration, specifically whether chemical cues in coastal vs oceanic seawater influenced their swimming orientation and their rate of development to juveniles. In total, 66% of pueruli actively swam toward coastal water rather than oceanic water (n = 41), indicating that they may use chemical cues in their settlement processes. Holding pueruli in coastal water vs artificial seawater did not expedite the development of pueruli to benthic juvenile stage, indicating that other cues could be important to the final settlement process. The present study suggests that chemical cues are being used in settlement processes during the onshore migration to settlement sites in this ecologically and economically important species.

Coastal marine upwelling famously supports elevated levels of pelagic biological production, but can also subsidize production in inshore habitats via pelagic‐benthic coupling. Consumers inhabiting macroalgae‐dominated rocky reef habitats are often considered to be members of a food web fuelled by energy derived from benthic primary production; conversely, they may also be subsidized by materials transported from pelagic habitats. Here, we used stable isotopes (δ13C, δ15N) to examine the relative contribution of pelagic and benthic materials to an ecologically and economically important benthivorous fish assemblage inhabiting subtidal macroalgae‐dominated reefs along ~1,000 km of the northern Chilean coast where coastal upwelling is active. Fish were isotopically most similar to the pelagic pathway and Bayesian mixing models indicated that production of benthivorous fish was dominated (median 98%, range 69–99%) by pelagic‐derived C and N. Although the mechanism by which these materials enter the benthic food web remains unknown, our results clearly highlight the importance of pelagic‐benthic coupling in the region. The scale of this subsidy has substantial implications for our basic understanding of ecosystem functioning and the management of nearshore habitats in northern Chile and other upwelling zones worldwide.