Physical Biological Coupling In Aquatic Ecosystems PDF Download

Phytoplankton form the basis of aquatic food webs and are responsible for almost half of the Earth's primary production. They represent an important indicator of water quality and are extremely sensitive to climate change. Physical processes in water bodies affect ecosystem functioning in a number of ways and phytoplankton readily respond to alterations in the physical environment. Hence, a deep knowledge of hydrodynamics and physical-biological coupling mechanisms in aquatic ecosystems is essential in understanding the structure of ecological communities and elucidating phytoplankton growth and succession patterns, which is of paramount importance for water quality management, especially in the light of a changing climate. This study explored the hydrodynamic mechanisms underlying phytoplankton community composition and responsible for maintaining bioproductivity in three very distinct aquatic systems: Lake Burragorang, Swan-Canning Estuary (both in Australia), and Lake Iseo (Italy). This was achieved through an integrated approach combining field data and three-dimensional modelling. Lake Burragorang is a reservoir formed in 1960 that represents the biggest water supply source to Sydney (Australia). This work has shown that low water levels as a consequence of climate change combined with an extreme rainfall event and associated high inflow volumes were responsible for a major cyanobacteria bloom that was the only algal bloom registered in the history of the reservoir. In the Swan-Canning Estuary, a highly urbanised micro-tidal salt-wedge estuary located in Perth (Australia), phytoplankton succession and the formation of algal blooms were shown to be strongly controlled by the timing and magnitude of freshwater inflows and their consequences to residence time, water column stratification, and salinity concentrations. Lastly, the work in Lake Iseo, a large, deep, and strongly stratified sub-alpine lake in Lombardy (Italy), has conclusively shown that the energy transfer from basin-scale internal waves down to high-frequency nonlinear internal waves is significant, implying nonlinear and nonhydrostatic processes need to be considered in order to accurately predict ecological responses to physical forcing. This is extremely important in deep, meromictic systems, where the breaking of high-frequency internal waves and resulting boundary mixing are most likely the main mechanisms of communication between hypolimnetic and epilimnetic waters, strongly controlling phytoplankton productivity in the euphotic layer. This study brings new insights into proper management strategies and demonstrates a thorough comprehension of physical-biological coupling mechanisms is crucial in order to understand and predict how different aquatic ecosystems will respond to extreme events and climate change.