Ecological effects of blooms of filamentous green algae in the littoral zone of an acid lake

Abstract

Ecological effects of blooms of filamentous green algae (FGA) were studied in an experimentally acidified Bake (pH 4.5) at the Experimental Lakes Area in northwestern Ontario, Canada. Blooms of FGA influenced the energy balance, chemical cycling, physical features, and biological conditions in the littoral zone. Photosynthetic capacity of the FGA, dominated by Zygogonium, was greater than that of acidified epilithon, the normally dominant littoral algal association, partially offsetting acidification-induced oligotrophication in the littoral zone. Intraand inter-annual variability of FGA growth was large, however, so that FGA were an unreliable energy source for the littoral food web. Nutrient uptake varied with the degree of FGA growth; e.g., FGA were occasionally the largest phosphorus pool in the epilirnnion. Nitrogen dynamics of FGA varied seasonally causing acidification in spring and summer, and alkalinization in fall. The blooms also affected epilimnetic cycling of dissolved inorganic carbon. Peak blooms prevented as much as 90% of the light from reaching the lake bottom. Local depletions of oxygen resulting from FGA decomposition also posed potential risks for animals using the HGA as habitat.RCsumC : Les effets Ccologiques de la prolifkration d'algues vertes (chlorophycCes filamenteuses) ont fait 190bjet d'Ctudes dans un lac expkrimentalement acidifiC (pH de 4,s) dans la region des lacs expCrimentaux du nord-ouest de 1'8ntario (Canada). Les prolifdrations d'algues vertes ont eu une incidence SUP le bilan knergktique, B e cycle chimique, les caractCristiques physiques et les conditions biologiques de B a zone Hittorale. La capacitC de photosynthkse des algues vertes, dsminCes par Zvgogonium, Ctait supCrieure h celle de 19Cpilithon acidifik, l'association algale qui dornine normalement dans la zone littorale, cornpensant en pai-tie 1901igotrophisation rksultant du processus d9acidification du littoral. Cependant, on a enregistre une grande variabilitk de la croissance des algues vertes au cours de l'annee et d9une annCe 2i l'autre, ce qui fait de ces algues une source d'knergie peu fiable pour le reseau trophique littoral. L'absorption des ClCrnents nutritifs varie avec le degrC de croissance des algues vertes; p. ex., les algues vertes csnstituaient parfois H a rCserve de phosphore la plus importante de lqCpilimnion. La dynamique de l'azote chez les algues vertes varie d'une saison B l'autre, entrainant une acidification au printemps et en CtC, et une alcalinisation en automwe. Les proliferations ont egalement nui au cycle du carbone inorganique dissous dans 1'Cpilimnion. Au cours des p&riodes de proliferation maximale, la proportion de I'kclairement qui we psuvait pas atteindre le fond du lac s9Clevait parfois h 98%. L'appauvrissement local en oxyg8ne resultant de la dCcomposition des aHgues vertes posait Cgalement des risques Cventuels pour les organismes utilisant les algues vertes comme habitat. [Traduit par Ia RCdaction]

Whole-lake algal responses to a century of acidic industrial deposition on the Canadian Shield

“…The characteristic proliferation of filamentous green algae in the littoral zones of anthropogenically acidified lakes (Turner et al 1995;Vinebrooke et al 2001) also likely contributed to pigment-inferred increases in post-industrial algal abundance in the acidified Killarney lakes. In particular, increased sedimentary chl b concentrations in Acid Lake, OSA Lake, George Lake, and Bell Lake after 1900 suggested that green algae became more abundant in these lakes following the onset of acid deposition.…”

“…Acid rain, climate warming, and increased ultraviolet-B (UVB; 280-320 nm wavelength) irradiance impact biodiversity of naturally species-poor communities in boreal lakes, which may reduce or destabilize vital ecosystem functions, such as primary production (Schindler 1995). For example, experimental acidification of boreal lakes caused significant loss of algal species, resulting in increased temporal variability of primary production (Turner et al 1995;Findlay et al 1999). However, primary production is not suppressed by experimental acidification because acid-tolerant species compensate for the extirpation of acid-sensitive competitors Klug et al 2000).…”

“…Whole-lake experiments ) and lake surveys (Vinebrooke 1996;Vinebrooke and Graham 1997) show that phytobenthos assemblages shift from cyanobacteria to filamentous green algae and diatoms with increasing water acidity. Benthic mats of filamentous green algae often proliferate and detach to form floating clouds, termed metaphyton, that shift primary production in the littoral zone from the phytobenthos to the overlying water column during late summer (Turner et al 1995;Vinebrooke et al 2001). Thus, anthropogenic acidification can cause long-term alteration of algal communities by changing their abundance, taxonomic composition, and spatial distribution in boreal lakes.…”

“…Pigment stratigraphies were used to determine if long-term cultural acidification of boreal lakes reduced or destabilized whole-lake algal abundance and taxonomic composition. This expectation was based on the welldocumented negative effects of anthropogenic acidification on algal diversity (Turner et al 1995;Vinebrooke and Graham 1997;Findlay et al 1999), and consequently, how a major loss of species can impair a community's ability to acquire resources and tolerate environmental stress and variability (Schindler 1995).…”

Response of benthic and planktonic algal biomass to experimental water-level manipulation in a prairie lakeshore wetland

“…The abundance of metaphyton is especially notable because it has been common during the 10-year period of the MERP project (Hosseini and van der Valk 1989b), but it is rare in the unmanipulated marsh (Goldsborough and Robinson 1996). Despite being commonly reported to flourish in response to anthropogenic acidification (Turner et al 1995) and eutrophication (Eiseltovh and Pokorn2~ 1994), relatively little is known of the ecological requirements of metaphytic algae. These results demonstrate that algae can be major contributors to total primary production in freshwater wetlands.…”