Accounting of ecosystem services from microalgae in wetlands of Shivamogga district, KarnatakaCite

Introduction

Ecosystem services are the benefits that ecosystems provide for human well-being (Haines-Young and Potschin, 2018), which include provisioning services, regulating services, and cultural services (de Groot et al., 2020; Ramachandra et al., 2019). Provisioning services describe the material or energy outputs directly derived from the wetland ecosystem, such as food , freshwater, fuelwood, raw materials, genetic and medicinal resources. Regulating services include benefits obtained from the regulation of ecosystem processes, such as carbon sequestration, air quality, moderation of extreme events, biological control with disease regulation, erosion prevention, water purification, and flood control. Cultural services are the non-material benefits from the ecosystems through spiritual enrichment, cognitive development, recreation, education and aesthetic experiences (Baskent, 2020; Magalhaes Filho et al., 2020).

Wetlands are the most productive ecosystems that support biodiversity and provide an array of ecosystem services. Wetland services include the provision of food (fish, fodder), water (domestic, irrigation), recreation, nutrient cycling, climate regulation, water purification, flood prevention, erosion control, aquifer recharge, carbon sequestration, and maintenance of biodiversity (Ramachandra et al., 2016; Barbier, 2013; Green and Elmberg, 2014). Nutrient cycling is a vital function that helps to maintain the productivity of an ecosystem (Ronnback et al., 2007). The quantification and valuation of wetland ecosystem services helps to understand benefits that humans receive from wetlands and encourages stakeholders to protect and restore degraded ecosystems, which helps to achieve sustainability goals. Stakeholders participation in the valuation studies help to identify the key ecosystem services, assess their values, and evaluate trade-offs involved in the use of various ecosystem services (Koko et al., 2020).

The review of studies pertaining to the assessment of the economic value of wetlands, reveal that market value approach was used for the valuation of provisioning services, whereas non-market values were adopted for regulating and cultural services. The annual value of the Begnas watershed system was $3.91 million (Thapa et al., 2020). The economic value of wetland ecosystem services from the Koshi Tappu wildlife reserve, Nepal amounted to 16 USD million/yr (Sharma et al., 2015). The average total economic value for Boeng Cheung Aek wetland is 30.12 million USD/yr, with values ranging from 15.71- 48.96 million USD/yr (Ro et al., 2020). The total economic value of wetland resources from polluted Varthur lake, Bangalore, Karnataka accounts to 118.98 Rs/ha/day (Ramachandra et al., 2011). The majority of wetlands in Bangalore are degraded due to unplanned rapid urbanization, with industrialization, population pressure, and pollution (Ramachandra et al., 2020; Ramachandra and Aithal, 2016). The degradation of wetlands hampers the various ecosystem services and, thus, reduces the economic value of wetlands. A comparative evaluation of a polluted lake (Amruthalli) and an unpolluted lake (Rachenahalli) showed the revenue of 20 Rs/ha/day in the Amruthalli lake and 10,435 Rs/ha/day in the Rachenahalli lake, Bangalore highlight the lowering of ecosystem services (which affect the livelihood of dependent population) due to pollution of wetlands (Ramachandra et al., 2005). Water pollution due to anthropogenic activities causes variations in species richness, community structure, trophic structure, and affects the health of aquatic organisms (U.S. EPA., 2002). Heavy metals, pesticide residues, and other pollutants adversely affect wetland biodiversity as they persist for longer periods in nature, have high bioaccumulation ability, and toxicity (Zhang et al., 2015). The factors that stimulate the eutrophication process include excessive amounts of nutrients (nitrogen and phosphorus) and organic matter, optimum temperature and light, longer retention time, and massive algal growth (Tang et al., 2020). A sudden rise in temperature can aggravate the eutrophication process, leading to microalgal blooms, fish kills, and the formation of dead zones in surface water (Bassi et al., 2014). Water pollution due to anthropogenic activities results in phytoplankton blooms that can degrade wetland ecosystem services by reducing drinking water availability, reducing recreational activity, and reducing biodiversity (Schallenberg et al., 2013).

Microalgae are the photosynthetic organisms and primary producers of aquatic ecosystems. Microalgae use light energy to convert carbon dioxide (CO₂) to organic compounds such as sugars (Asulabha et al., 2018). Macrophytes provide substrate for the growth of periphyton, which is consumed as food by grazing invertebrates and fish (Gopal, 2016). The growth rate of microalgae depends on light conditions and nutrient (nitrogen and phosphorus) exchanges (Juneja et al., 2013). The growth of microalgae, nutrient removal, and CO₂ sequestration are influenced by numerous biotic factors such as bacteria, viruses, fungi, and other consumers, as well as abiotic factors such as temperature, light, pH, nutrients, dissolved oxygen, and other toxic compounds or pollutants (Asulabha et al., 2022). Microalgae also help in water purification, wastewater treatment, and CO₂ sequestration with subsequent biomass and biofuel production. For the production of 1 kg of dry algae biomass, 1.83 kg of CO₂ is required, assuming a 50% carbon content of the algae (Ahmad et al., 2011). As a result, microalgae contribute to a low-cost, environmentally friendly nutrient removal process while also lowering greenhouse gas (GHG) emissions. Since microalgae provide valuable services to society, valuation of ecosystem services provided by microalgae in wetlands is necessary. The main objectives of the current study are: (a) to quantify various provisioning, regulating and cultural services from microalgae thriving in wetlands; (b) computation of total ecosystem supply value (TESV) and net present value (NPV) of freshwater wetland assets in the Shivamogga district of Karnataka.