Posts Tagged 'algae'



Decreasing pH affects seagrass epiphyte communities

Increasing CO2 in the atmosphere is affecting marine ecosystems, including seagrass beds. Epiphytes are a component of seagrass ecosystems. Epiphytes make a significant contribution as important primary producers in the food chain. Increasing atmospheric CO2 leads to a decrease in oceanic pH that can result in an unfavorable environment for the epiphytic community. This study was conducted to determine the effect of increasing CO2 on seagrass epiphytic communities and biomass. Using a field experiment, we manipulated dissolved carbon dioxide to 800 – 1000 ppm in line with the forecast increase in atmospheric CO2 levels in the year 2100. In situ C02 manipulations were conducted using an open-top mesocosm. The CO2 enrichment was conducted by adding CO2 at a concentration around 800 – 1000 ppm. This CO2 was injected directly using a pump and hose to the acrylic mesocosm chamber. Epiphyte community structure was affected, with an increase in the abundance of filamentous algae but a decrease in the coralline algae community in the CO2 enriched treatment units. Overall, CO2 enrichment had no effect on epiphyte biomass.

Continue reading ‘Decreasing pH affects seagrass epiphyte communities’

Effects of environmental stressors on a habitat forming macroalga over evolutionary and ecological time scales

Fucus vesiculosus is a keystone species in the North Atlantic and Baltic Sea; any changes in its distribution or physical structure could have broad-reaching implications on many coastal ecosystems. It is therefore important to understand both how this important species has evolved in the past and adapted to historical changes in the environment but also how future environmental stress and changes will affect this species. When stress, for example from environmental change, affects a population, traits that make individuals more likely to survive will remain in the population. This is the fundamental basis of evolution, occurring over both short and long time scales. Climate change is
liable to exert a strong selective pressure on many species as it changes the environment inhabited by those species.

Continue reading ‘Effects of environmental stressors on a habitat forming macroalga over evolutionary and ecological time scales’

Diverse responses of sporophytic photochemical efficiency and gametophytic growth for two edible kelps, Saccharina japonica and Undaria pinnatifida, to ocean acidification and warming

Highlights

• Increased pCO2 enhanced sporophytic photosynthesis of S. japonica and U. pinnatifida.
• Increased pCO2 inhibited gametophytic growth of these two kelps.
• Ocean acidification and warming represent major threats to kelp mariculture.
• U. pinnatifida showed higher productivity in warmer ocean than S. japonica.

Abstract

Ocean acidification and warming represent major environmental threats to kelp mariculture. In this study, sporophytic photochemical efficiency and gametophytic growth of Saccharina japonica and Undaria pinnatifidawere evaluated under different pCO2 levels (360, 720, and 980 ppmv) and temperatures (5, 10, 15, and 20 °C for sporophytes; 15 and 20 °C for gametophytes). Sporophytic photochemical efficiencies of both kelps were significantly greater at 720 ppmv than at 360 and 980 ppmv. Female gametophytes of both kelps grew significantly better at 360 ppmv than at higher pCO2 levels. The growth of U. pinnatifida gametophytes was significantly greater at 20 °C than at 15 °C, while no significant difference was observed for the growth of S. japonica. These results indicate that increased pCO2 stimulated sporophytic photochemical efficiency while inhibited gametophytic growth of these kelps, which might negatively affect their seedling cultivation. U. pinnatifida exhibited higher productivity in warmer ocean than S. japonica.

Continue reading ‘Diverse responses of sporophytic photochemical efficiency and gametophytic growth for two edible kelps, Saccharina japonica and Undaria pinnatifida, to ocean acidification and warming’

Seagrasses, the unique adaptation of angiosperms to the marine environment: effect of high carbon and ocean acidification on energetics and ion homeostasis

As a functional group, seafrasses form highly productive ecosystems present along the coasts of all continents (except Antarctic), where they rival tropical rainforests and coral reefs in ecosystem services (Costanza et al., 1997; Fourqurean et al., 2012). Unfortunately, seagrasses are diminishing worldwide and several studies confirm a lack of appreciation for the value of these systems (Cullen-Unsworth et al., 2014). Since the last century, the effects of climate change on natural and agricultural terrestrial plant communities have already received significant attention.

Continue reading ‘Seagrasses, the unique adaptation of angiosperms to the marine environment: effect of high carbon and ocean acidification on energetics and ion homeostasis’

Calibration of the pH-δ11B and temperature-Mg/Li proxies in the long-lived high-latitude crustose coralline red alga Clathromorphum compactum via controlled laboratory experiments

A solid understanding of global oceanic change throughout Holocene time is needed to contextualize and interpret recent observations of rapid warming (Moore, 2016), ocean acidification (Popova et al., 2014Qi et al., 2017), increasing meltwater input (Halfar et al., 2013Notz and Stroeve, 2016) and circulation changes (Liu et al., 2017Rahmstorf et al., 2015Yang et al., 2016) in the Arctic and subarctic Oceans. Precisely reconstructing acidification and temperature variations throughout the Holocene will provide a vital context for interpreting current environmental changes and future climate projections in the region. However, existing paleoenvironmental reconstructions are sparse and uncertain, largely owing to limited availability of high fidelity paleoceanographic archives, such as marine carbonates, in high latitude waters. Coralline algae of the genus Clathromorphum have emerged as key candidates for reconstructing high-latitude environmental variability at annual to sub-annual resolution. Here, we present the first empirical calibrations of boron isotope-pH and Mg/Li-temperature relationships within the long-lived, crustose coralline red alga Clathromorphum compactum. Calibration experiments were performed in triplicate, growing wild-collected specimens for four months at three controlled temperatures (6.4 – 12.4 oC) and four pCO2 conditions (352 – 3230 ppm), to test the effects of these environmental parameters on the isotopic and elemental composition of the algal skeleton.We find that boron isotopes within the skeleton of C. compactum (δ11Bcc) are well correlated with δ11B of seawater borate (δ11Βborate), defining the following equation: δ11Βcc (2σ) = 1.46 (0.06) δ11Βborate + 6.91 (0.72). This equation can be used to reconstruct δ11Βborate of the coralline alga’s ambient seawater, from which past seawater pH can be calculated. We also identified a strong correlation between skeletal Mg/Li ratio and seawater temperature, defined by the equation: Mg/Li (2σ) = 0.17 (0.02) temperature (oC) + 1.02 (0.16). Therefore, despite the strong biological control that this species appears to exert on calcification site pH (elevated 1.0-1.6 pH units above seawater pH, inferred from δ11Bcc > δ11Βborate), and the apparent relationship between skeletal extension rate and skeletal Li/Ca and Mg/Ca, the δ11Bcc and Mg/Li ratios of the coralline alga’s skeleton strongly and significantly respond to ambient seawater pH and temperature, respectively. These results support the use of δ11B and Mg/Li within C. compactum for pH and temperature reconstructions of northern high-latitude oceans.

Continue reading ‘Calibration of the pH-δ11B and temperature-Mg/Li proxies in the long-lived high-latitude crustose coralline red alga Clathromorphum compactum via controlled laboratory experiments’

pH variability exacerbates effects of ocean acidification on a Caribbean crustose coralline alga

Crustose coralline algae (CCA) are among the most sensitive marine taxa to the pH changes predicted with ocean acidification (OA). However, many CCA exist in habitats where diel cycles in pH can surpass near-future OA projections. The prevailing theory that natural variability increases the tolerance of calcifiers to OA has not been widely tested with tropical CCA. Here, we assess the response of the reef-building species Lithophyllum congestum to stable and variable pH treatments, including an ambient control (amb/stable). The amb/variable treatment simulated an ambient diel cycle in pH (7.65–7.95), OA/stable simulated constant low pH reflecting worst-case year 2100 predictions (7.7), and OA/variable combined diel cycling with lower mean pH (7.45–7.75). We monitored the effects of pH on total calcification rate and photophysiology (maximum quantum yield) over 16 weeks. To assess the potential for acclimatization, we also quantified calcification rates during the first (0–8 weeks), and second (8–16 weeks) halves of the experiment. Calcification rates were lower in all pH treatments relative to ambient controls and photophysiology was unaffected. At the end of the 16-week experiment, total calcification rates were similarly low in the amb/variable and OA/stable treatment (27–29%), whereas rates declined by double in the OA/variable treatment (60%). When comparing the first and second halves of the experiment, there was no acclimatization in stable treatments as calcification rates remained unchanged in both the amb/stable and OA/stable treatments. In contrast, calcification rates deteriorated between periods in the variable treatments: from a 16–47% reduction in the amb/variable treatment to a 49–79% reduction in the OA/variable treatment, relative to controls. Our findings provide compelling evidence that pH variability can heighten CCA sensitivity to reductions in pH. Moreover, the decline in calcification rate over time directly contrasts prevailing theory that variability inherently increases organismal tolerances to low pH, and suggests that mechanisms of tolerance may become limited with increasing time of exposure. The significant role of diel pH cycling in CCA responses to OA indicates that organisms in habitats with diel variability could respond more severely to rapid changes in ocean pH associated with OA than predicted by experiments conducted under static conditions.

Continue reading ‘pH variability exacerbates effects of ocean acidification on a Caribbean crustose coralline alga’

Ulva prolifera green tide outbreaks and their environmental impact in the Yellow Sea, China

The Ulva prolifera green tides in the Yellow Sea, China, which have been occurring since 2007 are a serious environmental problem attracting worldwide attention. Despite extensive research, the outbreak mechanisms have not been fully understood. Comprehensive analysis of anthropogenic and natural biotic and abiotic factors reveals that human activities, regional physicochemical conditions and algal physiological characteristics as well as ocean warming and biological interactions (with microorganism or other macroalgae) are closely related with the occurrence of green tides. Dynamics of these factors and their interactions could explain why green tides suddenly occurred in 2007 and decreased abruptly in 2017. Moreover, the consequence of green tides is serious. The decay of macroalgal biomass could result in hypoxia and acidification, possibly induce red tide, and even have long lasting impact on coastal carbon cycles and ecosystem. Accordingly, corresponding countermeasures have been proposed in our study for future reference in ecosystem management strategy and sustainable development policy.

Continue reading ‘Ulva prolifera green tide outbreaks and their environmental impact in the Yellow Sea, China’


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Ocean acidification in the IPCC AR5 WG II

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