Zooplankton Behaviour Influences Vulnerability to ocean acidification: Results from an Individually-Based Simulation Model

Chair: Ivan Nagelkerken

Paul McElhany (1), Simone Alin (2), Vathsala DeSilva (1), Julie Keister (3), Tarang Khangaonkar (4), Tanika Ladd (5), Anna McLaskey (3), Wen Long (4)

1 NOAA Northwest Fisheries Science Center, Seattle, WA, 98112, USA
2 NOAA Pacific Marine Environmental Laboratory, Seattle, WA, 98115, USA
3 University of Washington, School of Oceanography, Seattle, WA, 98105
4 Pacific Northwest National Laboratory, Seattle, WA, 98109
5 University of California, Santa Barbara, CA, 93106

Background
The vulnerability of a species to ocean acidification is a function of its sensitivity to carbonate chemistry conditions (e.g., pH) and the likelihood that it is exposed to deleterious carbonate chemistry conditions in the field. Understanding the likelihood of exposure requires integrating information on the spatial-temporal patterns of marine carbonate chemistry and the details of species’ movement behaviour. The carbonate chemistry of the Salish Sea (NE Pacific) is highly variable, and the relative vulnerability of zooplankton species in this ecosystem may be strongly dependent on differences in their behaviour.

Methods
We used an individually-based approach to simulate the movement of zooplankton through a circulation/water quality model of the Salish Sea. The high resolution circulation model included carbonate chemistry parameters under both current conditions and anticipated future DIC loads. Zooplankton were modelled with a variety of different behaviours that correspond to behaviours observed in local species.

Findings
Species that exhibit more surface-oriented behaviours experience relatively higher pH conditions than species undergoing daily vertical migrations, though this difference can be small relative to the influence of their location within the Salish Sea. The variability in carbonate chemistry condition exposure differed between species whose horizontal movement was current-driven and species with random direction swimming behaviour. A tendance to move toward or away from a non-carbonate environmental factor (e.g. temperature, oxygen, chlorophyll) affected likelihood of exposure to deleterious carbonate chemistry conditions.

Conclusions
Species-specific movement behaviours can have a substantial influence on their vulnerability to ocean acidification by influencing species exposure to various carbon chemistry conditions.