Assembleias aquáticas na avaliação da eutrofização e valoração de serviços ecossistêmicos em reservatórios do semiárido

Abstract

Anthropic eutrophication is a threat to aquatic ecosystems, as it affects community composition, ecosystem structure, and functioning. As a consequence, there is a loss of ecosystem goods and services that are essential to human well-being. Therefore, there is a need for studies that integrate the biological assessment of eutrophication with the evaluation of ecosystem goods and services, as well as the local population’s perception of the benefits provided by aquatic organisms. Among the tools that can be used in this integration are eco-exergy indices, which reflect the information and energy stored in ecosystems, as well as the monetary valuation of ecosystem goods and services through the Willingness to Pay (WTP) of the benefited population, and the Intrinsic Value, which corresponds to the ecosystem’s value outside the human perspective. In this context, this thesis aims to evaluate eutrophication in semiarid reservoirs, relating it to biodiversity responses (using the Hill series), to thermodynamic indices (eco-exergy and specific eco-exergy), and to the estimated monetary value (intrinsic value and willingness to pay) of aquatic assemblages of periphytic algae and benthic macroinvertebrates. This thesis is composed of two chapters, with the following guiding hypotheses: Chapter 1 has the following hypotheses (i) Eutrophication leads to the dominance of resistant taxa and the establishment of indicator species in both assemblages, as it acts as an environmental filter selecting for tolerant taxa; and (ii) The assemblages exhibit congruent diversity responses (Hill series indices), with an increase in diversity under eutrophic conditions, while thermodynamic indices do not reflect eutrophication due to the distribution of dominant species with high biomass. Chapter 2 presents the following hypothesis (i) Intrinsic value, measured through the eco-exergy index, is capable of reflecting water quality in monetary valuation, while valuation through Willingness to Pay (WTP) is not. This is because periphytic algae and benthic macroinvertebrates are little-seen organisms that provide ecosystem services not perceived by most of the population, leading to a low perception of value regardless of water quality. As for the results, in Chapter 1 we found that taxonomic thresholds were able to reflect the responses of periphytic algae and benthic macroinvertebrate assemblages to eutrophication, even when these differences were not reflected in thermodynamic indices. This result is explained by the nature of the reservoirs, which are anthropized systems subject to multiple stressors. In Chapter 2, we found that the intrinsic value of the periphytic algae and benthic macroinvertebrate assemblages, measured through the eco-exergy index, reflected the water quality of the reservoirs in the monetary valuation process. The highest intrinsic value was found in the system with the best water quality. The WTP did not reflect water quality. Most riparian residents did not perceive any benefits arising from the aquatic assemblages. Furthermore, services were perceived within the three CICES categories: Regulation and Maintenance, Provisioning, and Cultural. With this thesis, we demonstrate that TITAN is an efficient tool for assessing eutrophication in reservoirs and that intrinsic value is a promising tool in the valuation of ecosystem services, as it reflects environmental quality.