Role of jellyfish in the plankton ecosystem revealed using a global ocean biogeochemical model

Rebecca M Wright,Corinne Le Quéré,Erik Buitenhuis,Sophie Pitois,Mark J Gibbons

doi:10.5194/bg-18-1291-2021

Abstract

Abstract. Jellyfish are increasingly recognised as important components of the marine ecosystem, yet their specific role is poorly defined compared to that of other zooplankton groups. This paper presents the first global ocean biogeochemical model that includes an explicit representation of jellyfish and uses the model to gain insight into the influence of jellyfish on the plankton community. The Plankton Type Ocean Model (PlankTOM11) model groups organisms into plankton functional types (PFTs). The jellyfish PFT is parameterised here based on our synthesis of observations on jellyfish growth, grazing, respiration and mortality rates as functions of temperature and jellyfish biomass. The distribution of jellyfish is unique compared to that of other PFTs in the model. The jellyfish global biomass of 0.13 PgC is within the observational range and comparable to the biomass of other zooplankton and phytoplankton PFTs. The introduction of jellyfish in the model has a large direct influence on the crustacean macrozooplankton PFT and influences indirectly the rest of the plankton ecosystem through trophic cascades. The zooplankton community in PlankTOM11 is highly sensitive to the jellyfish mortality rate, with jellyfish increasingly dominating the zooplankton community as its mortality diminishes. Overall, the results suggest that jellyfish play an important role in regulating global marine plankton ecosystems across plankton community structure, spatio-temporal dynamics and biomass, which is a role that has been generally neglected so far.

Highlights

Gelatinous zooplankton are increasingly recognised as influential organisms in the marine environment – not just for the disruptions they can cause to coastal economies – and as important consumers of plankton (Lucas and Dawson, 2014), which is a food source for many marine species (Lamb et al, 2017), and as key components in marine biogeochemical cycles (Crum et al, 2014; Lebrato et al, 2012)
This study focuses on Cnidaria, which contribute 92 % of the total global biomass of gelatinous zooplankton (Lucas et al, 2014)
The other gelatinous zooplankton groups, Tunicata and Ctenophora, are excluded from this study, because there are far fewer data available on their biomass and vital rates than for Cnidaria; they only contribute a combined global biomass of 8 % of total gelatinous zooplankton (Lucas et al, 2014). Cnidaria are both independent enough from other gelatinous zooplankton and cohesive enough to be represented as a single plankton functional type (PFT) for global modelling (Le Quéré et al, 2005)

Summary

Introduction

Gelatinous zooplankton are increasingly recognised as influential organisms in the marine environment – not just for the disruptions they can cause to coastal economies (fisheries, aquaculture, beach closures, power plants, etc.; Purcell et al, 2007) – and as important consumers of plankton (Lucas and Dawson, 2014), which is a food source for many marine species (Lamb et al, 2017), and as key components in marine biogeochemical cycles (Crum et al, 2014; Lebrato et al, 2012). The other gelatinous zooplankton groups, Tunicata and Ctenophora, are excluded from this study, because there are far fewer data available on their biomass and vital rates than for Cnidaria; they only contribute a combined global biomass of 8 % of total gelatinous zooplankton (Lucas et al, 2014). Cnidaria are both independent enough from other gelatinous zooplankton and cohesive enough to be represented as a single plankton functional type (PFT) for global modelling (Le Quéré et al, 2005). For the rest of this paper, pelagic Cnidaria are referred to as jellyfish

Objectives

Methods

Results

Discussion

Conclusion