Computing marine plankton connectivity under thermal constraints

Abstract

Ocean currents are a key driver of plankton dispersal across the oceanic basins. However, species specific temperature constraints may limit the plankton dispersal. We propose a methodology to estimate the connectivity pathways and timescales for planktonspecies with given constraints on temperature tolerances, by combining Lagrangian modeling with network theory. We demonstrate application of two types of temperature constraints: thermal niche and adaptation potential and compare it to thesurface water connectivity between sample stations in the Atlantic Ocean. We find that non-constrained passive particles representative of a plankton species can connect all the stations within three years at the surface with pathways mostly along the major ocean currents. However, under thermal constraints, only a subset of stations can establish connectivity. Connectivity time increases marginally under these constraints, suggesting that plankton can keep within their favorable thermal conditions by advecting via slightly longer paths. Effect of advection depth on connectivity is observed to be sensitive to the width of the thermal constraints, along with decreasing flow speeds with depth and possible changes in pathways.

Global mesozooplankton communities show lower connectivity in deep oceanic layers

“…These findings are in line with those obtained by Siokou et al (2019) in the Mediterranean Sea, who observed differentiation between Eastern and Western Mediterranean mesozooplankton communities at lower mesopelagic and bathypelagic depths, but no differentiation at epipelagic and upper mesopelagic layers. These results point to lower connectivity between deep-sea mesozooplankton communities than between communities from upper oceanic layers, which may be driven by limitations in the dispersal of mesozooplankton assemblages at the ocean depths due to prevailing weaker oceanic currents and water mixing in the deep sea compared to the surface (Manral et al, 2023;Reid, 1981Reid, , 1994-in agreement with previous findings for picoeukaryotes (Villarino et al, 2022). Our findings add further evidence on the major role of oceanic currents in shaping zooplankton dispersal and connectivity at a global scale, not only at epipelagic layers as previously reported (Richter et al, 2020;Villarino et al, 2018;Watson et al, 2011), but, for the first time for mesozooplankton, also at the ocean depths.…”

“…We hypothesise: i) that unexplored oceanic regions, such as the deep sea, harbour a higher proportion of hidden mesozooplankton diversity than those from upper layers, ii) that mesozooplankton communities are subjected to vertical and horizontal oceanic gradients at a global scale, which generate global biogeographic patterns, and iii) that mesozooplankton spatial distribution and connectivity differ at the different ocean layers, with higher dissimilarity between deep-sea communities than between communities at upper layers due to the average weaker deep-sea currents compared to surface ones (Manral et al, 2023;Reid, 1994).…”

Using biophysical modelling and marine connectivity to assess the risk of natural dispersal of non-indigenous species to comply with the Ballast Water Management Convention

“…Fully pelagic species such as planktonic organisms generally have high dispersal potential between very distant locations (e.g. the entire Atlantic Ocean) given enough time although environmental constraints such as temperature or salinity may impose limitations in connectivity (Manral et al 2023). Zoogeographical evidence suggests that the dispersal of many pelagic species is more likely to be limited by their ability to maintain viable populations rather than hydrographic barriers (Noris 2000).…”

Haline Tolerance of Stomatopod (Crustacea) Larvae and Pelagic Dispersal of Two Common Species in the Western Atlantic

“…Zooplankton organisms have limited motility for long distances and depend on ocean currents to move horizontally. Advection of plankton by ocean currents is the primary factor driving the ecosystem dynamics in the upper pelagic zone (Manral et al., 2023). Oceanographic processes that affect plankton transport and distribution act in a continuum of spatial scales.…”