The impacts of past, present and future ocean chemistry on predatory planktonic snails.

Deborah Wall-Palmer,Linda K Dämmer,Karel Bakker,Paula Ramos-Silva,Erica Goetze,Lisette Mekkes,Katja T C A Peijnenburg,Elza Duijm

doi:10.1098/rsos.202265

Abstract

The atlantid heteropods represent the only predatory, aragonite shelled zooplankton. Atlantid shell production is likely to be sensitive to ocean acidification (OA), and yet we know little about their mechanisms of calcification, or their response to changing ocean chemistry. Here, we present the first study into calcification and gene expression effects of short-term OA exposure on juvenile atlantids across three pH scenarios: mid-1960s, ambient and 2050 conditions. Calcification and gene expression indicate a distinct response to each treatment. Shell extension and shell volume were reduced from the mid-1960s to ambient conditions, suggesting that calcification is already limited in today's South Atlantic. However, shell extension increased from ambient to 2050 conditions. Genes involved in protein synthesis were consistently upregulated, whereas genes involved in organismal development were downregulated with decreasing pH. Biomineralization genes were upregulated in the mid-1960s and 2050 conditions, suggesting that any deviation from ambient carbonate chemistry causes stress, resulting in rapid shell growth. We conclude that atlantid calcification is likely to be negatively affected by future OA. However, we also found that plentiful food increased shell extension and shell thickness, and so synergistic factors are likely to impact the resilience of atlantids in an acidifying ocean.

Highlights

In the marine realm, predators at all levels, from sharks to mesozooplankton, have a critical impact on the structure and function of ecosystems, and selective predators in particular are essential for maintaining biodiversity [1,2]
Dissolved Inorganic Carbon (DIC) analyses for the third control carboy failed, results are only reported for the two control carboys with a full suite of water chemistry data
Differences in pH between the treatments were relatively small, and aragonite super saturation was maintained across all experiments, the juvenile atlantids responded differently to the different ocean chemistry conditions

Summary

Introduction

Predators at all levels, from sharks to mesozooplankton, have a critical impact on the structure and function of ecosystems, and selective predators in particular are essential for maintaining biodiversity [1,2]. The atlantid heteropods (Atlantidae, Pterotracheoidea) are one such family of selective predators in the plankton. These carnivorous holoplanktonic gastropods feed primarily on another key group of planktonic gastropods, the shelled pteropods (Thecosomata) [3,4]. The atlantid shell is already present upon hatching [3] and is likely important at the larval stage for physical protection, and as ballast to allow rapid escape by sinking. Almost nothing is known about the shell structure of atlantids and their mechanisms of calcification [7,8], despite likely being affected by imminent ocean changes, in particular rapid contemporary changes in ocean chemistry, and especially in the early life stages [9,10,11,12]

Objectives

Methods

Results

Conclusion