HOW TOUGH ARE SCLEROPHYLLS

10.1006/anbo.1993.1043ANNALS OF BOTANY714343-34

An ex-situ mesocosm study of emergent macrophyte effects on phytoplankton communities

© 2019 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany. Although the ability of submerged macrophytes to inhibit phytoplankton growth has been studied extensively, little has been done for emergent macrophytes. We investigated the effects of four emergent macrophyte species (Brachiaria mutica, Ipomoea aquatica, Ischaemum muticum, Ipomoea pes-caprae) on the phytoplankton community of a eutrophic tropical reservoir with cyanobacterial dominance. A mesocosm experiment was conducted over 28 days by growing macrophytes on a substrate of expanded clay pellets with 18 % surface area coverage in tanks filled with water from a reservoir with phytoplankton dominated by cyanobacteria. Nutrient levels (total nitrogen and total phosphorus concentrations), total phytoplankton biomass and the structure of phytoplankton community were compared over the course of the experiment. All four species of macrophytes did not significantly reduce the total nitrogen, total phosphorus, or phytoplankton biomass. The Ipomoea pes-caprae treatment, however, led to a shift in the phytoplankton community structure with an increased abundance of Aphanocapsa sp., a small-celled colonial cyanobacterium often found dominant in post-restoration phytoplankton communities. This study shows that using the current approach and a planting density reflecting natural conditions, the four macrophyte species tested may not necessarily reduce phytoplankton biomass, but their introduction may lead to phytoplankton community changes

Evaluating seaweed farming as an eco-engineering strategy for ‘blue’ shoreline infrastructure

Ecological Engineerin

Comparative study of six emergent macrophyte species for controlling cyanobacterial blooms in a tropical reservoir

© 2019 Elsevier B.V. Interactions between macrophytes and phytoplankton have been studied extensively in temperate water bodies, but far less attention has been paid to those for emergent macrophytes in the tropics. We investigated the effects of six emergent macrophyte species (Brachiaria mutica, Ipomoea aquatica, Sphagneticola trilobata, Ludwigia adscendens, Pandanus amaryllifolius and Persicaria barbata) on the phytoplankton community of a tropical reservoir using ex situ experiments with multiple planting densities (Treatment 1: 0.108, Treatment 2: 0.24, Treatment 3: 0.40, Treatment 4: 0.58 g dry weight L −1 ) in 100-L mesocosms. Chlorophyll a (as a proxy of total phytoplankton biomass) and phytoplankton community structure were examined. The initial phytoplankton community (average chlorophyll a: 20.36 ± 0.69 µg L −1 ) was dominated by cyanobacteria: Planktolyngybya, Pseudanabaena and Cylindrospermopsis (average relative biovolume 0.68 ± 0.03). Over four weeks, L. adscendens (Treatments 3 and 4) and P. barbata (Treatments 2 to 4) significantly reduced chlorophyll a concentrations by 3.29–6.69 µg L −1 compared to the controls. Comparing species effects over four weeks for Treatment 4, P. barbata significantly lowered chlorophyll a concentrations compared to I. aquatica while there were no significant differences between all other species. All treatments of L. adscendens and P. barbata significantly reduced the relative biovolume of cyanobacteria in the phytoplankton communities by 0.19–0.39 compared to the controls. The highest-density treatments of all six macrophyte species led to significant shifts in the phytoplankton community structure by reducing the relative abundance of filamentous cyanobacteria (Planktolyngbya, Pseudanabaena) and/or increasing the relative abundance of cryptomonads (Chroomonas, Rhodomonas). This study shows the potential of emergent macrophyte species, especially L. adscendens and P. barbata, to reduce total phytoplankton biomass and cyanobacterial dominance in tropical water bodies, and a range of plant densities which were effective

Tropical macrophytes promote phytoplankton community shifts in lake mesocosms: relevance for lake restoration in warm climates

Macrophytes can be crucial for maintaining clear water conditions in temperate shallow lakes. However, their restorative potential and role in regulating phytoplankton remains uncertain in tropical lakes. We investigated the effects of emergent (Ludwigia adscendens and Persicaria barbata) and submerged (Vallisneria spiralis) macrophytes on the phytoplankton community of a turbid tropical reservoir. Through two in situ mesocosm experiments (~ 1000 l capacity) lasting 4 weeks, we (1) determined the effects of macrophyte density on phytoplankton biomass and composition, and (2) compared these effects between emergent and submerged macrophytes. In Experiment 1, macrophyte treatments reduced phytoplankton biomass and increased water clarity in a density-dependent manner. Only the ‘high density’ treatment (300 g/m2 emergent and 650 g/m2 submerged macrophytes) induced a taxonomic and functional shift from an initial community dominated by turbid water-adapted filamentous cyanobacteria to one dominated by clear water-adapted green algae and cryptophytes. In Experiment 2, emergent and submerged macrophytes reduced phytoplankton biomass and distinctly altered taxonomic and functional composition, with submerged macrophytes inhibiting Microcystis and stimulating cryptophyte taxa. Our results indicate that macrophytes can induce substantial phytoplankton community shifts in turbid tropical lakes, demonstrating the potential to assist in the reversal from turbid to clear water states during restoration efforts

Home gardening in Singapore: A feasibility study on the utilization of the vertical space of retrofitted high-rise public housing apartment buildings to increase urban vegetable self-sufficiency

10.1016/j.ufug.2022.127755Urban Forestry and Urban Greening78127755-12775

Stingers in a strange land: South American freshwater stingrays (Potamotrygonidae) in Singapore

10.1007/s10530-009-9663-5Biological Invasions1282385-2388BLIN