Ecological and Physiological Controls of Species Composition in Green Macroalgal Blooms

Abstract

Green macroalgal blooms have substantially altered marine community structure and function, specifically by smothering seagrasses and other primary producers that are critical to commercial fisheries and by creating anoxic conditions in enclosed embayments. Bottom-up factors are viewed as the primary drivers of these blooms, but increasing attention has been paid to biotic controls of species composition. In Washington State, USA, blooms are often dominated by Ulva spp. intertidally and Ulvaria obscura subtidally. Factors that could cause this spatial difference were examined, including competition, grazer preferences, salinity, photoacclimation, nutrient requirements, and responses to nutrient enrichment. Ulva specimens grew faster than Ulvaria in intertidal chambers but not significantly faster in subtidal chambers. Ulva was better able to acclimate to a high-light environment and was more tolerant of low salinity than Ulvaria. Ulvaria had higher tissue N content, chlorophyll, chlorophyll b: chlorophyll a, and protein content than Ulva. These differences suggest that nitrogen availability could affect species composition. A suite of five grazers preferred Ulva to Ulvaria in choice experiments. Thus, bottom-up factors allow Ulva to dominate the intertidal zone while resistance to grazers appears to allow Ulvaria to dominate the subtidal zone. While ulvoid algae are in the same functional-form group, they are not functionally redundant.

Abiotic factors influencing biomass accumulation of green tide causing Ulva spp. on Pyropia culture rafts in the Yellow Sea, China

“…Salinity at the sites of both lowest (Haitou) and highest (Rudong) algal growth was similar (26.5 to 30.4) while salinity at Sheyang was lower and varied greatly (12.0 to 22.7) consistent with the rainfall seasonality and the close proximity (8 km) of the mouth of the Sheyang River. Salinity can affect the growth of Ulva, but they tolerate a wide range (Martins et al, 1999;Taylor et al, 2001;Nelson et al, 2008). We did not find any evidence that salinity explained Ulva biomass patterns in this study.…”

World’s largest macroalgal bloom caused by expansion of seaweed aquaculture in China

“…These green algae are able to respond rapidly to excess nutrients especially when water temperature conditions are favourable to their growth (Fletcher, 1996;Hernández et al, 1997;Valiela et al, 1997;Raffaelli et al, 1998;Morand and Merceron, 2005). Typically green-tides are characterised by choking of waterways in the immediate area of the bloom and subsequent local wind and tide driven local deposition on the shore, and this can be destructive to coastal marine habitats (e.g., seagrass) and cause economic losses to marine industries (e.g., fisheries and tourism) (Nelson et al, 2008).…”

Effects of Environmental Factors on Zoospore Release and Early Growth of the Green Tide Alga Cladophora albida

“…C. albida blooms are most likely to occur under these optimal environmental conditions, as plentiful zoospore release and rapid germling growth lead to population growth. (Taylor et al, 2001;Nelson et al, 2008;Human et al, 2016), (Lin et al, 2008), · (Lin et al, 2008;Zhang et al, 2016). , (Ulva clathrata) (Ulva lactuca) 2014 (El Shoubaky, 2015), 4-6 (Pedersen and Borum, 1997).…”

“…, (Moreno-Marín et al, 2016), (Nelson et al, 2008). , 2008 (Ulva prolifera) 500 (US$ 40 million) (Ye et al, 2011;Gao et al, 2016).…”

“…(e.g., Ulva armoricana, Ulva rotundata) (e.g., Ulva intestinalis, Chaetomorpha valida) , (Taylor et al, 2001;Nelson et al, 2008;Choi et al, 2010 …”