Comparing community size patterns and food web structure in eutrophic temperate and sub-tropical freshwater systems.

Increasing human pressure is accelerating environmental change throughout the world, threatening water security for humans and aquatic biodiversity. One example is the widespread nutrient pollution of aquatic ecosystems which may result in biodiversity loss, changes in ecosystem processes and functional attributes such as secondary production and declining water quality. In temperate zones our understanding of the functional attributes of freshwater systems, the ecological services that they provide, and their response to nutrient enrichment is relatively advanced but in tropical/ sub-tropical systems data, and therefore understanding, are limited. We do not know whether the aquatic community responses, and the underlying biological processes, of both areas will be similar or different. These are central questions because understanding how environmental processes control resource availability (in this case clean water) is critical for the responsible use of that resource. We will initiate a long term partnership between Roehampton University (RU) and Federal University of Santa Catarina (UFSC) to compare freshwater systems in temperate and sub-tropical areas across a gradient of nutrient concentrations, community structure (presence of cyanobacteria) and over time. We will identify similarities and differences in aquatic community response to eutrophication in these two distinct regions and evaluate the resultant impact on water quality. Initially we will jointly explore a detailed 8 year data set (2007-2014) for the Peri basin (Santa Catarina Island, southern Brazil) held by Petrucio and compare it with datasets for temperate freshwater systems held by Robertson and Reiss. The Peri basin is a protected area and is used for drinking water supply for a significant part of the conurbation of Florianopolis. It is beginning to show signals of eutrophication and water quality degradation with an increasing dominance and biomass of a widespread toxic cyanobacterium. Our partnership will further develop this data by measuring individual body sizes for organismal groups comprising the freshwater communities within the Peri basin across space and time. Body size is a crucial determinant of the structure of many ecological communities and is a new 'common currency' in ecological research enabling comparison of community structure and responses to disturbance within and between systems. This data will then be used to determine higher level community parameters such as body size spectra, secondary production and food web properties for the Peri basin and determine how these vary through time with changing nutrient concentrations and how this may effect water quality. The collaborators will additionally exchange and develop joint research ideas through informal discussions and seminars but also through the planned workshops and field trips in Brazil, RU conference and visits to freshwater research centres in the UK and by attendance and presentations at the British Ecological Society annual meeting.

The welfare, health and economic development of human populations is dependent on an abundant and inexpensive supply of good quality water; a fundamental human right. However, increasing population pressure and economic development in Brazil are contributing to declining water quality including nutrient enrichment (eutrophication) and the development of toxic cyanobacteria. Our partnership will develop a fundamental understanding of the responses of sub-tropical freshwater systems (biodiversity, ecosystem processes and services, structure and functional attributes) to eutrophication in comparison to those of temperate systems. As the nature of the responses of the aquatic community to eutrophication will influence water quality, this knowledge will underpin appropriate responses to declining water quality in the region. Thus beneficiaries include water authorities, national regulators, policy makers and indeed the general public.