OCE-PRF Track 1 (Broadening Participation): What drives population connectivity in the open sea?

Iacchei Matthew J, Honolulu HI

Investigators

Abstract

As earth's climate changes, populations of both terrestrial and marine species are responding in one of three major ways: by adapting to new environments, by moving to a more favorable environment, or by perishing. While evaluating these responses to climate change has been ongoing for terrestrial species and some coastal marine species for at least a decade, the data on open ocean zooplankton has been limited. This gap in knowledge is significant, as zooplankton form the base of the open ocean food chain, and zooplankton are hypothesized to be some of the most sensitive marine species to environmental change. This project focuses on the copepod Pleuromamma xiphias, a dominant migratory zooplankton in tropical and subtropical waters worldwide, and how populations of P. xiphias are affected by environmental change. Results will be important for understanding how open ocean food webs and nutrient cycles are changing with time, and how this in turn may affect the abundance and distribution of species higher in the food chain that are vital to our food resources. In conjunction with this work, the fellow will mentor traditionally underrepresented groups of students in Hawai'i at three critical educational levels: when they are initially becoming excited about science and learning about the role of science in society (K-12), when they are deciding whether or not to pursue science as a career (undergraduate students), and when they require strong mentorship to succeed in their scientific pursuits (graduate students). In marine systems, planktonic species have been proposed as sensitive indicators of environmental change. With short generation times, populations of these pelagic organisms often show tight coupling between physical forcing and biological response. However, the question remains whether plankton have the capacity to adaptively evolve with respect to rapidly changing ocean regimes, whether they will decrease in population abundance and geographic extent, or whether they will alter their primary habitat preferences. To understand the adaptive capacity of plankton populations, we first need to understand the spatiotemporal scale of gene exchange for the species of interest, and identify the factors that determine the boundaries of those scales. The proposed project will use genome-wide data from a pelagic copepod (Pleuromamma xiphias), coupled with multiple environmental variables collected across a spatio-temporal gradient, to assess what determines the scale of population connectivity in the open sea, and infer how these factors influence the response of Atlantic Ocean P. xiphias populations to climate change. Specifically, the fellow will examine the following hypotheses: 1) Biological and physical environment are selective forces shaping population structure in P. xiphias; 2) Migration rate is high among sites within the North and South Atlantic gyres, but low at the poleward edges of each gyre and across the equator; 3) P. xiphias populations will be increasing in abundance and expanding toward the poleward range of their distribution, while sites at the equatorial edges will be undergoing bottlenecks. This work will be conducted under the mentorship of Erica Goetze, PhD in the School of Ocean and Earth Science and Technology (SOEST) at the University of Hawai'i at Manoa. Each of the comparisons (genes, sites, time points, environmental variables) will contribute incremental insights into the genetic structuring of pelagic zooplankton. Combined, they have the potential to transform the way we think about population connectivity in the open ocean, and shed new light on the potential adaptive capacity of pelagic copepods in a changing climate.