Algal richness and life‐history strategies are influenced by hydrology and phosphorus in two major subtropical wetlands

Abstract

. We used the intermediate disturbance hypothesis, and the species-energy theory to explain 35 algal richness patterns, and the competitive, stress-tolerant, ruderal (CSR) framework to 36 classify indicator taxa. We collected algal samples, environmental data and information 37 expected to influence community structure (water depth, relative depth change, P 38 concentrations, hydroperiod, and habitat type) over several years at sites representing a broad 39 range of environmental characteristics. To account for sample size differences, we estimated 40 algal richness by determining the asymptote of taxon accumulation curves. Using multiple 41 regression analysis, we assessed if and how water depth, depth change, P, hydroperiod, and 42 habitat type influence richness within each wetland. We then compared the strength of the 43 relationships between these controlling features and richness between wetlands. Using 44 indicator species analysis on relative abundance data, we classified C, S and R indicator taxa 45 with shorter/longer hydroperiod, and lower/higher P concentrations. 3. In either wetland, we did not observe the negative unimodal relationship between site-47 specific richness and water depth change that was expected following the intermediate 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Okavango's natural pulse, and increasing freshwater flow in the Everglades would help 52 protect these wetlands' algal diversity. Chlorophyta richness (Okavango), and total, 53 Bacillariophyta, Chlorophyta and cyanobacteria richness (Everglades) increased with higher 54 P concentrations, as per species-energy theory. In the Okavango, we classified 6 C and 49 R 55 indicator taxa (e.g. many planktonic Chlorophyta), and, in the Everglades, 15 C, 1 S, and 9 R 56 taxa (e.g. benthic Bacillariophyta and planktonic/benthic Chlorophyta), and 1 stress-and 57 disturbance-tolerant cyanobacterium species. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 facilitate each other, thus increasing biomass production efficiency (Cardinale et al., 2009). 77As the loss of biodiversity threatens ecosystem functioning (Ptacnik et al., 2008; Cardinale et 78 al., 2011), fundamental research is needed to identify factors that increase and/or maintain the their food webs is a key task for freshwater ecologists (de Tezanos Pinto et al., 2015). 86In flood-pulsed wetlands, the alternation of wet and dry seasons determines nutrient 87 release upon rewetting, and generates a dynamic mosaic of aquatic and terrestrial 88 environments with high habitat heterogeneity (Junk, Bayley & Sparks, 1989). Hydrology, 89 nutrients, and habitat type in turn influence the richness of algae, effective ecological ...

Identifying environmental drivers of benthic diatom diversity: the case of Mediterranean mountain ponds

“…In particular, periphytic diatoms constitute one of the most important components of algal assemblages in aquatic habitats in terms of diversity, biomass and ecosystem metabolism. However, the understanding of how diatom communities respond to environmental changes is still limited (Teittinen et al, 2016), and accordingly, the recent literature has a focus on identifying factors that control the diversity of diatoms in freshwater ecosystems (Marazzi et al, 2017).…”

Beyond the Hydro-Regime: Differential Regulation of Plant Functional Groups in Seasonal Ponds

“…and Nitella spp., became dominant across many of the treatments after two years, likely reducing aquatic plant cover via competitive exclusion for resources (e.g., light and space) [24,27,[42][43][44]. This is often a result of the formation of algal mats, which are associated with P retention and reduction in light attenuation [24,[44][45][46][47]. During unstable hydroperiods, algae can increase in growth [40,48], which can also stabilize the spatial distribution of nutrients and water fluctuations, promoting plant establishment during the terrestrial hydro-phase [24,47].…”

“…This is often a result of the formation of algal mats, which are associated with P retention and reduction in light attenuation [24,[44][45][46][47]. During unstable hydroperiods, algae can increase in growth [40,48], which can also stabilize the spatial distribution of nutrients and water fluctuations, promoting plant establishment during the terrestrial hydro-phase [24,47]. Excess nutrients released from algal mats during the terrestrial hydro-phase are directly associated with an increase in exotic plants, facilitating increases in exotic thatch [24,25,27,29,47].…”

Fire regime of peatlands in the Angolan Highlands

“…The Angolan Highlands are part of an extensive interior plateau, characterised by a vast peneplain of Kalahari sand (Goyder et al, 2018 ; Huntley et al, 2019 ), and is the primary water source region for the Okavango Delta, a UNESCO World Heritage Site (Marazzi et al, 2017 ). The climate is strongly seasonal, with hot, wet conditions during the summer months from October to May, and cool, dry conditions during the winter months from June to September (Abiodun et al, 2019 ; Huntley et al, 2019 ).…”