Quantifying spatiotemporal variability in zooplankton dynamics in the Gulf of Mexico with a physical-biogeochemical model

Abstract

<jats:p>Abstract. Zooplankton play an important role in global biogeochemistry and their secondary production supports valuable fisheries of the world's oceans. Currently, zooplankton abundances cannot be estimated using remote sensing techniques. Hence, coupled physical-biogeochemical models (PBMs) provide an important tool for studying zooplankton on regional and global scales. However, evaluating the accuracy of zooplankton abundance estimates from PBMs has been a major challenge as a result of sparse observations. In this study, we configure a PBM for the Gulf of Mexico (GoM) from 1993–2012 and validate the model against an extensive combination of in situ biomass and rate measurements including total mesozooplankton biomass, size-fractionated mesozooplankton biomass and grazing rates, microzooplankton specific grazing rates, surface chlorophyll, deep chlorophyll maximum depth, phytoplankton specific growth rates, and net primary production. Spatial variability in mesozooplankton biomass climatology observed in a multi-decadal database for the northern GoM is well resolved by the model with a statistically significant (p </jats:p>

Trade-offs between risks of predation and starvation in larvae make the shelf break an optimal spawning location for Atlantic Bluefin tuna

“…The IBM developed here is forced with 20 years (1993–2012) of realistic hydrodynamics, zooplankton biomasses, temperature, water clarity, and ambient light fields obtained from a three-dimensional physical-biogeochemical model (NEMURO-GoM; Shropshire et al ., 2020). NEMURO-GoM is a highly-modified version of the NEMURO biogeochemical model (Kishi et al , 2007) run in an offline configuration of the MIT general circulation model (MITgcm, Marshall et al , 1997; McKinley et al , 2004) and forced with daily-averaged dynamical fields from a ~4-km, data-assimilative, Hybrid Coordinate Ocean Model (Chassignet et al , 2009).…”

“…For example, advective losses are likely a significant source of mortality for coastal demersal species whose larvae require specific benthic substrates for settlement. In contrast, starvation is expected to be a large source of larval mortality for oceanic species like Atlantic Bluefin tuna (ABT), which spawn in warm oligotrophic regions of the Gulf of Mexico (GoM) where zooplankton biomass is low (~2–6 mg C m −3 ) and variable (Shropshire et al, 2020). Because quantifying larval mortality in the field is exceedingly difficult, individual based models (IBMs) provide a strategy for investigating the relationships between larval mortality and environmental conditions.…”

“…To investigate the impact of mortality as a mechanism for driving larval abundances in the GoM, we developed a spatially explicit, Lagrangian, individual-based model (IBM) that simulates dispersal, growth and mortality with an emphasis on the period from egg to postflexion. Larval mortalities due to starvation and predation are quantified using high-resolution, spatiotemporally-varying zooplankton fields supplied by a physical-biogeochemical model (Shropshire et al, 2020). The goals for this study were to: 1) estimate annual larval mortality; 2) compare the relative magnitudes of predation and starvation; and 3) identify environmental factors and regions in the GoM that minimize larval mortality.…”

Lateral Advection Supports Nitrogen Export in the Oligotrophic Open-Ocean Gulf of Mexico

“…Since the oligotrophic GoM has previously been compared to the mid-ocean gyres due to similar biogeochemical properties (e.g. DCM, oligotrophic, low biomass) 20,30,37 , it may be reasonable to consider the applicability of our results to these oceanic regions. The mid-ocean gyres are both larger than the GoM and may have less average kinetic energy (leading to circulation time-scales of months-years, rather than weeks).…”

Plankton food webs of the Gulf of Mexico spawning grounds of Atlantic Bluefin tuna

“…The open-ocean Gulf of Mexico (GoM) is a nutrient-poor, low plankton biomass region (Biggs & Ressler, 2001, Damien et al, 2018, Shropshire et al, 2020. Nevertheless, it is an important region for spawning and larval development of many commercially-important fishes (Cornic et al, 2018, Kitchens & Rooker, 2014, Lindo-Atichati et al, 2012, Rooker et al, 2013, Rooker et al, 2012.…”