Life history mediates the association between parasite abundance and geographic features

Abstract

Although parasites are ubiquitous in marine ecosystems, predicting the abundance of parasites present within marine ecosystems has proven challenging due to the unknown effects of multiple interacting environmental gradients and stressors. Furthermore, parasites often are considered as a uniform group within ecosystems despite their significant diversity. We aim to determine the potential importance of multiple predictors of parasite abundance in coral reef ecosystems, including reef area, island area, human population density, chlorophyll‐a, host diversity, coral cover, host abundance and island isolation. Using a model selection approach within a database of more than 1,200 individual fish hosts and their parasites from 11 islands within the Pacific Line Islands archipelago, we reveal that geographic gradients, including island area and island isolation, emerged as the best predictors of parasite abundance. Life history moderated the relationship; parasites with complex life cycles increased in abundance with increasing island isolation, while parasites with direct life cycles decreased with increasing isolation. Direct life cycle parasites increased in abundance with increasing island area, although complex life cycle parasite abundance was not associated with island area. This novel analysis of a unique dataset indicates that parasite abundance in marine systems cannot be predicted precisely without accounting for the independent and interactive effects of each parasite's life history and environmental conditions.

Empirically tuned theory reveals why symbiont abundance ‘mite’ vary across hosts

“…However, likely owing to their small size and often inconspicuous nature, very few details are known regarding symbiont abundance compared to non‐symbiotic (i.e. free‐living) organisms (Mestre et al., 2019; Williams et al., 2022). Even less attention on this topic has been given to functionally non‐parasitic symbionts (Jovani et al., 2017).…”

Black Spot Syndrome in ocean surgeonfish: using video-based surveillance to quantify disease severity and test environmental drivers on Curacao reefs

“…Data for the site-level environmental factors were derived from existing information for Curaçao collected during an intensive, island-wide survey in 2015 (see Waitt Insitute 2017, Sandin et al 2022). This marine scientific assessment included detailed information on the physical and biological environments at 122 sites along the leeward shore, for which the island was divided into eight zones based on a combination of biological, physical, and anthropogenic characteristics.…”

“…Nutrient pollution had a positive influence on the observed severity of BSS. As an indicator of sewage and domestic runoff, isotopically heavy nitrogen (delta-15-N) within algal tissue tends to be highest in the waters near the main city of Willemstad and lowest on lesspopulated eastern and western ends of the island (Klaus et al 2004, Lapointe & Malin 2011, Sandin et al 2022. Runoff of nutrients and other pollutants can enhance parasite infection through multiple mechanisms.…”

“…Compared to other islands in the Caribbean, Curaçao has relatively high coral cover and fish biomass (Sandin et al 2008). Nonetheless, factors such as coral cover, fish abundance, and water quality vary considerably among sites along the leeward coastline (Sandin et al 2022), with generally greater coral cover, higher fish abundance, and less pollution toward the far east side of the island (Waitt Institute 2017). Impacts associated with human development are particularly concentrated around the urban center of Willemstad and the major commercial harbor of St. Annabaai, which collectively represent important sources of runoff for nutrients and other pollutants (e.g., Gast et al 1999, Klaus et al 2007.…”

“…This marine scientific assessment included detailed information on the physical and biological environments at 122 sites along the leeward shore, for which the island was divided into eight zones based on a combination of biological, physical, and anthropogenic characteristics. As part of this survey, Sandin et al (2022) published an extensive dataset on fish biomass, coral cover, benthic assemblages, fishing pressure, pollution, and site-specific physical features, which was used here to develop potential predictor variables. Previous research on marine parasites has highlighted the influence of both the biotic community and habitat-related differences on infection abundance, including fish abundance, fishing pressure, coral cover, pollution, and water movement (Grutter 1998, Byers et al 2008, Lacerda et al 2017, Williams et al 2022.…”