Assessing macroinvertebrate responses in the Mooi River Catchment within and ecological water requirements framework

Autor: Nyongo, Zafika Zimtoti Maud
Přispěvatelé: Malherbe, W., Kemp, M., 25425293 - Malherbe, Charl Wynand (Supervisor), 20797192 - Kemp, Mathilde (Supervisor)
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Popis: M (Environmental Management), North-West University, Potchefstroom Campus Freshwater ecosystems; rivers in particular, are amongst some of the most threatened ecosystems on earth which is directly linked to the fact that the ecological integrity of rivers and other freshwater ecosystems is a direct reflection of all the activities taking place in the areas they drain. Rivers become vulnerable by being exposed to a variety of disturbance associated with rapidly growing human populations. People depend on water for activities such as irrigation, electricity generation and waste disposal. South Africa adopted a new water legislation that promoted equity, sustainability, representatively and efficiency through water management by decentralizing, new local and regional institutions; where registration and licencing is necessary. The role of Resource Directed Measures (RDM) is to ensure the protection of water resources, by protecting ecosystem functioning and maintaining a desired state of health of aquatic and groundwater dependent ecosystems. Resource Quality Objectives (RQO) offer a direction which management could pursue in order to achieve desired protection of a resource while also expressing the acceptance or unacceptance of impacts and activities on a water resource. In RDM, Ecological Water Requirements (EWR) basically quantify the water regime in terms of quality, quantity and timing that is required to ensure the adequate functioning and future persistence of aquatic ecosystems. The Mooi River is a situated in the North-West Province of South Africa, within the Upper Vaal Water Management Area. The Wonderfontein Spruit sub-catchment is the north-eastern reach, dominated by mining and farming activities in the lower parts. The Loop Spruit sub-catchment is the eastern reach, dominated by livestock as well as crop farming and joins the Mooi River downstream of the town of Potchefstroom. The Mooi River system is important for maintaining the quality of potable water of Potchefstroom and surrounding areas. However, this system is under constant threat from anthropogenic pollution arising from both agricultural and mining activities in its catchment. The successful management of river ecosystems and changes in river systems resulting from human or natural influences, need to be assessed and measured Macroinvertebrates make good candidates to assess aquatic ecosystem quality since they can respond in many ways to environmental stresses. The Macroinvertebrate Response Assessment Index (MIRAI) is an approach that should be undertaken to relate drivers and the resultant habitat to the aquatic macroinvertebrate condition. The approach uses macroinvertebrate abundance and presence, as well as macroinvertebrate preferences for flow modifications, habitat preferences and water quality when determining the Present Ecological Status (PES) of macroinvertebrates. The result is the Ecological Category (EC), which is a basic indication of the river condition as a percentage of what it should be or the expected. Taxonomic based approaches apply several metrics such as single metrics and indices and multi metric indices developed and used in biomonitoring based on macroinvertebrate community structure. Family level taxonomic determinations in biomonitoring have been the focal point of most research but with lack in integrated taxonomic and trait based evaluations. Taxonomy based descriptions are limited in their ability to define ecological responses to stress Most traits are predictable in the manner in which they will react to stress because trait response to disturbance can be put in context, but also possess discriminatory capabilities. Trait Based Approaches are a promising area for the use of biomonitoring data in causal diagnosis by use of phenotypic characters of taxa in the area of traits analysis. This study tested the hypothesis that the macroinvertebrate assemblage responses and functional structures will reflect the presence of disturbances in the ecosystem of the Mooi River catchment. Five reaches were established by grouping 21 sampled sites along the catchment. Collected macroinvertebrates were classified up to family level and subjected to the MIRAI to determine the Ecological Categories of the reaches. The water quality metrics for MR1 (32.6%), MR2 (32.2%), MR3 (31.3%) showed the highest deviation from reference conditions, and MR4 and MR5 were 43.4% and 41.2% respectively. The EC of four reaches, namely MR1 (46.73%), MR2 (45.51%), MR3 (44.64%) and MR4 (52.62%) were in Ecological Class D which is a largely modified state; and water quality was the most altered metric, as measured by the response of the macroinvertebrate assemblages. In MR5, both water quality and flow metrics were had a score of 41.2%, which meant that both these metrics were in the lower limits of Class D. The MR5 bordered on being seriously modified Ecological Class D/E. Traits and ecological preferences information were obtained mainly from a South African macroinvertebrate trait database. Nine macroinvertebrate traits with 43 categories were assigned, which were habitat preference, velocity preference, water quality preference, hydraulic habitat preference, functional feeding groups, respiration, body size, body shape, as well as locomotion. The general outline of the catchment after application of macroinvertebrate traits showed the relative highest abundances being allocated to GSM taxa and were most abundant in MR2 (44.94%); taxa who prefer very slow flows (˂0.1m/s) who were most abundant in MR2; highly tolerant taxa most abundant in MR5; taxa that is indifferent to hydraulic habitat conditions and was most abundant in MR3; predators most abundant in MR4; gill breathers who were most abundant in MR3; taxa with variable body shapes most abundant in MR3; small-sized macroinvertebrates (˃5-10 mm) most abundant in MR3 as well as taxa who are swimmers that were most abundant in MR2. The results confirm the presence of impacts associated with various anthropogenic activities already documented in the Mooi River catchment and therefore suggest that monitoring of the catchment be strategic and adaptive to EWR because trait information hold potential to also inform the RQO. This study concluded that the implementation of macroinvertebrate traits along with other commonly used EWR methods could be valuable towards the quality of assessments for water resource management. Masters
Databáze: OpenAIRE
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