Response of Florida Shelf Ecosystems to Climate Change

Florida Shelf Geochemistry

Laboratory/Experimental Studies

Introduction

Laboratory experiments will assess changes in pH, pCO₂, and seawater carbonate chemistry on calcifying organisms that contribute to Florida Shelf sediments.

Single celled protozoa (Foraminifera), calcifying algae (Halimeda) and microbes represent the closest link to the environment and the environmental change. Little is known about the response of these calcifiers to increasing atmospheric CO₂, yet they may provide the earliest indication of water column change. They are the proverbial canary in a coal mine. Laboratory experiments examine the response of elevated CO₂ and reduced carbonate saturation on west Florida shelf foraminifera and calcifying green algae.

Laboratory experiments are being conducted at realistic future levels of pCO₂ in enclosed microcosms to assess the effects that changes in pH, pCO₂, and seawater carbonate chemistry will have on aragonitic green algae and benthic foraminiferal survival, calcification rates and shell morphology. Two important larger foraminiferal species and algal Halimeda are targeted. These species are abundant on carbonate shelves around Florida, where their shells and plates significantly contribute to shelf sedimentation. The foraminifera include the high-Mg-calcite Archaias angulatus and the calcitic Amphistegina gibossa. A preliminary set of experiments to assess growth, calcification and survival rates of Halimeda, Archaias, and Amphistegina in temperature- and light-controlled environmental chambers are being performed.

Additional historical archived samples of Halimeda from the last 60 years have been analyzed for ultra-structural changes via image analysis. These archived samples are being compared with results revealed in laboratory experiments.