[A-HW24] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

[AHW24-05] Southern Urban Hydrosystem Syndrome in Marikina Watershed Revealed by Taxonomic and Functional Diversity of Benthic Macroinvertebrates

*Kamille Nacalaban Poblete¹, Dimple May Gianne Q. Dumaguit¹, Elfritzson M. Peralta^1,2,3, Francis S. Magbanua⁴, Rey Donne S. Papa^1,2,3, Noboru Okuda^5,6 (1.Department of Biological Sciences, College of Science, University of Santo Tomas, España Boulevard, Manila, 1015, Philippines, 2.The Graduate School, University of Santo Tomas, España Boulevard, Manila, 1015, Philippines, 3.Research Center for the Natural and Applied Sciences, University of Santo Tomas, España Boulevard, Manila, 1015, Philippines, 4.Institute of Biology, University of the Philippines Diliman, Quezon City, 1101, Philippines, 5.Research Center for Inland Seas, Kobe University, Japan, 6.Research for Humanity & Nature, Japan)

Keywords:Biomonitoring, Functional feeding group, Longitudinal variation, Philippines, Urban ecology

Urban-related activities have long been recognized to generate environmental stressors that increasingly imperil the bio-physicochemical conditions of lotic ecosystems. Although this general pattern is globally observable, the Southern Urban Hydrosystem Syndrome differentiates the varying mechanisms and magnitudes of its consequences among economic and climatic regions. In developing countries, environmental pressures and impacts on tropical rivers are more apparent relative to temperate rivers of developed countries. However, there is a limited study on the effects of anthropogenic activities on the taxonomy and function of biological communities in an urban-impacted river of a developing tropical country. To examine the state of an urban-impacted river of a developing tropical country, this study aimed to examine the shift in benthic macroinvertebrates' taxonomic and functional structure through the different environmental variables and land-use practices in the Marikina Watershed. A total of 21 stream sites with different land use classifications (7 undisturbed, 7 agricultural, and 7 residential) and its corresponding environmental and macroinvertebrates’ taxonomic data (n = 4739) were analyzed. Using relevant articles and sources, the identified macroinvertebrates were classified into their respective functional feeding groups (FFGs). Ultimately, multivariate analyses explained the possible relationships between variables. Post hoc and canonical correlation analysis results revealed that undisturbed sites hold the highest taxon richness (p = 0.02) and diversity indices (p < 0.01). Moreover, undisturbed sites constitute sensitive taxa such as Afronurus sp., Caenis sp., and Sparsorythus sp. as a result of its significantly higher dissolved oxygen (DO) (p = 0.02) and pH (p = 0.02) levels than residential and agricultural sites, respectively. By contrast, residential sites were represented by pollution-tolerant taxa such as Chironomus sp. and are signified by its lower DO (p = 0.02) and higher mean (±SE) conductivity (348.81 ± 42.20) levels indicating a disturbed stream condition. Significant differences in the FFGs percent abundance were observed among land uses except for shredders (SH). Collector-filterers (CF) were the most abundant in undisturbed sites (p = 0.03), scrapers (SC) (p = 0.01) and predators (PR) (p = 0.02) for agricultural sites, while collector-gatherers (CG) dominated the residential sites (p = 0.01). The redundancy analysis tri-plot provided evidence on how the riparian-modified areas altered the trophic structure, as evident in the distinction between undisturbed and agricultural and residential sites. CF, CG, SH, and PR characterized the fast-flowing undisturbed streams, whereas the highly elevated agricultural streams having minor signs of contamination were associated with the presence of SC. Overall, the Marikina Watershed effectively illustrates how a tropical stream ecosystem in the Global South responds to the impacts of ongoing urbanization. The research findings reveal how the local government should focus on reducing anthropogenic stressors and boosting the conservation efforts in impacted streams to improve biodiversity and ecosystem functions.