Functional ecology of marine macrobenthic communities

Author: Orlando Lam-Gordillo

Lam-Gordillo, Orlando, 2022 Functional ecology of marine macrobenthic communities, Flinders University, College of Science and Engineering

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Marine biodiversity is rapidly decreasing worldwide due to human-induced pressures. Climate change, habitat fragmentation, and pollution are the main drivers of biodiversity loss, modifying the abundance, composition and distribution of marine species, and thus the functioning of ecosystems. Over the last decade, assessments on Biodiversity and Ecosystem Functioning have become topical for understanding how changes in biodiversity affect the functioning and services of ecosystems. However, gaps persist in the knowledge of macrobenthic communities’ functional ecology in southern temperate ecosystems. This PhD project aimed to understand the functional ecology of benthic communities and investigate the relationship between ecosystem functioning and marine macrobenthic fauna. This thesis provides a global framework on ecosystem functioning and functional approaches, a macrobenthic functional trait database with a step-by-step guide to assist future functional assessments, and a comprehensive implementation of the functional approaches into surveys and experiments to describe macrobenthic functional patterns, sediment nutrient cycling, and buffering capacity of estuarine ecosystems to nutrient loads.

Chapter 2 presents a global review on the topic of ecosystem functioning and functional approaches of marine macrobenthic fauna. A new research weaving method was used. This analysis provided suggestions for unifying the research field, a coherent terminology, methodology and metrics to be used in future, and the application of a generalized framework including the interlinkages among biological traits, ecosystem processes, and ecosystem functioning in marine macrobenthic fauna research. Chapter 3 introduces the South Australian Macrobenthic Traits (SAMT) database, the first comprehensive assessment of macrobenthic fauna traits in temperate Australian waters. Information for >250 macrobenthic taxa was provided, including outcomes from a fuzzy coding procedure for trait classification. An R package for using and analysing the SAMT database was also developed. This study includes an intuitive flow chart for assessing ecosystem functioning highlighting the utility of the SAMT database. Chapter 4 presents taxonomic and functional patterns of benthic macrofauna, and their relationship with environmental conditions. This study elucidated idiosyncratic functional and taxonomic patterns, and the need for complementary perspectives of taxonomic and functional metrics to obtain a holistic understanding of the functioning in marine sediments. Chapter 5 evaluates changes in macrobenthic fauna, in relation with sediment biogeochemistry across an estuarine-to-hypersaline lagoon ecosystem. This study revealed that macrobenthic communities and functional traits change across an extreme salinity gradient, which correlated with changes in sediment biogeochemistry. This chapter advances the understanding of this relationship, and further highlights the importance of preserving healthy benthic communities to mitigate eutrophication and ensure the functioning of estuarine benthic ecosystems. Chapter 6 presents an in situ experiment to investigate whether the bioturbating activity of benthic macrofauna can improve biogeochemical conditions in hostile (i.e. hypersaline, sulfide-rich) sediments. This study indicated that bioturbation by macrobenthic fauna influenced sediment biogeochemistry and remediated hostile conditions in sediment over time, highlighting the importance of benthic macrofauna for improving resilience, and supporting the functioning of estuarine ecosystem.

The integration of the five data chapters demonstrated the functional ecology of benthic communities, providing key knowledge for further functional assessments in southern temperate regions. It also highlighted the importance of including functional perspectives to improve management and conservation plans that ensure healthy functioning of benthic ecosystems.

Keywords: Ecosystem functioning, functional diverisity, macroinvertebrates, functions, benthos, Australia.

Subject: Biological Sciences thesis

Thesis type: Doctor of Philosophy
Completed: 2022
School: College of Science and Engineering
Supervisor: Sabine Dittmann