Photoacclimation in a tropical population of Cladophora glomerata (L.) Kützing 1843 (Chlorophyta) from southeastern Brazil

Abstract

Photoacclimation of photosynthesis was investigated in a tropical population of C. glomerata (São Paulo State, southeastern Brazil, 20° 48' 24" S and 49° 22' 24" W) by chlorophyll fluorescence parameters and chlorophyll a content. Plants were acclimated to two levels of irradiance: low (65 ± 5 mmol.m -2 .s -1 ) and high (300 ± 10 mmol.m -2.s -1 ) and exposed short-term (4 days) and long-term (28 days) under a light-dark cycle of 12:12 hours. Photosynthesis-irradiance (PI) curves revealed distinct strategies of photoacclimation. In long-term exposure, plants acclimated by altering the photosynthetic units (PSU) number and keeping fixed the PSU size, revealed by increased rates of maximum photosynthesis (P max ), lower photosynthetic efficiency (alpha) and higher values of the saturation parameter (I k ) under high irradiance. The short-term acclimation strategy consisted of changing the PSU size, with a fixed number of PSUs, as revealed by similar P max but higher alpha and lower I k under low irradiance. Chlorophyll a contents followed the general pattern reported in green algae of higher concentrations under lower irradiance. Dark/light induction curves revealed consistently higher values of potential quantum yield under low irradiance. Initial and final values showed a higher recovery capacity in the short (84.4-90.6%) term exposure than in the long-term case (81.4-81.5%). ETR (electron transport rate) and NPQ (non-photochemical quenching) values were consistently higher under low irradiance. ETR showed a continuous and steady increase along the light exposure period in the short and long-term experiments, whereas NPQ values revealed a rapid increase after 15 seconds of light exposure, kept a slightly increasing trend and stabilized in most treatments. Lower photosynthetic performance (ETR) and recovery capacity of potential quantum yield were observed, particularly in long-term exposure, suggesting that this population is constrained by the typical high light environment of tropical regions.Keywords: acclimation, Cladophora, light, macroalgae, photosynthesis, tropical. ) e expostas a curto período (4 dias) e longo período (28 dias) em fotoperíodo de 12 horas. Curvas de fotossíntese-irradiância (FI) revelaram estratégias distintas de fotoaclimatação. Plantas expostas a longo período aclimataram pela alteração do número de unidades fotossintéticas (UF) e mantiveram fixo o tamanho das UF. Estas características foram reveladas por menores taxas de fotossíntese máxima (F max ), menor eficiência fotossintética (alfa) e valores mais altos do parâmetro de saturação (I k ) em alta irradiância. A estratégia de aclimatação em curto período consistiu em mudança no tamanho das UF, com número fixo de UF, conforme revelado por taxas semelhantes de fotossíntese máxima (F max ), maiores valores de alfa e menores de I k em baixa irradiância. Os conteúdos de clorofila a seguiram o padrão geral reportado para algas verdes de maiores concentrações em baixa irradiância. Curvas de indução escuro/luz revelaram valores consi...

The Genus Cladophora Kützing (Ulvophyceae) as a Globally Distributed Ecological Engineer

“…Cladophora exposed to high irradiance displayed decreased quantum yield of PS II (assessed by chl a fluorescence), increased chl a: chl b ratios, and higher amounts of xanthophyll-cycle pigments than in lower irradiances. Similar light acclimation strategies were evident in C. glomerata collected from a nutrient-rich stream in SE Brazil (Bautista and Necchi-J unior 2008). Such light acclimation and tolerance to high light reported for N. Baltic Sea C. glomerata, relative to other coastal macroalgae (Choo et al 2004) and broad tolerance of irradiance, temperature and salinity reported for C. dalmatica in southern U.K. (Taylor et al 2001), may allow Cladophora to cope with seasonal changes in water level or turbidity, and contribute to invasive behavior in some habitats.…”

“…Cladophora exposed to high irradiance displayed decreased quantum yield of PS II (assessed by chl a fluorescence), increased chl a : chl b ratios, and higher amounts of xanthophyll‐cycle pigments than in lower irradiances. Similar light acclimation strategies were evident in C. glomerata collected from a nutrient‐rich stream in SE Brazil (Bautista and Necchi‐Júnior ). Such light acclimation and tolerance to high light reported for N. Baltic Sea C. glomerata , relative to other coastal macroalgae (Choo et al.…”

Lumostatic strategy for microalgae cultivation utilizing image analysis and chlorophyll a content as design parameters

“…This is because the initial cell concentrations for all the experiments were so low that the four constant light intensities used inhibited the photosynthetic rate of the microalgae cells (Adir et al, 2003;Ragni et al, 2008). In addition to photoinhibition, the microalgae cells also underwent photoacclimation, a strategy to cope with high light intensities and maintain a constant photosynthetic efficiency (Bautista and Necchi-Júnior, 2008;Grobbelaar and Kurano, 2003;MacIntyre et al, 2002). The higher the light intensity, the longer the photoacclimation time and consequently a longer lag phase duration.…”

The epiphytic microbiota of the globally widespread macroalga Cladophora glomerata (Chlorophyta, Cladophorales)

“…Auer and Canale (1982) showed that at optimum irradiance and temperature, C. glomerata in Lake Huron achieved a net growth rate of 0.6·d −1 when P was not limiting, i.e., could increase its mass by about 60% per day. Cladophora can use dissolved carbon dioxide or bicarbonate as an inorganic carbon source (Choo et al, 2002) and is able to rapidly acclimate to changes in irradiance (Ensminger et al, 2000a, 2000b; Bautista and Necchi‐Júnior, 2008). Laboratory experiments indicate that optimum irradiances for freshwater C. glomerata are 300–600 µmol photons·m −2 ·s −1 for freshwater C. glomerata (Graham et al, 1982), consistent with field observations that this alga commonly occupies littoral areas ranging from 0 to 10 or more meters depth, depending on water clarity.…”