Posts Tagged 'phytoplankton'

Late Quaternary coccolith weight variations in the northern South China Sea and their environmental controls

Highlights

• High-resolution records of coccolith weights in the South China Sea.

• Different coccolithophore species show different variations in calcification.

•Coccolithophore calcification in nature is supposed to be affected by multiple factors.

Abstract

Coccolithophores are one of the most abundant and widespread groups of calcifying plankton and have attracted extensive study in terms of their likely response to ocean acidification. Conflicting results concerning coccolithophore calcification have been reported from both experimental and field studies. Due to their minute size, it is difficult to estimate the amount of calcite in coccoliths. Here we apply the SYRACO system to analyzing the weights and lengths of coccoliths produced by the dominant coccolithophore family Noëlaerhabdaceae. We obtain high-resolution coccolith weight and length records of GEO (Gephyrocapsa oceanica) and SPC (Emiliania huxleyi and small Gephyrocapsa spp.) groups from sediment core MD05-2904 in the northern South China Sea (SCS) over the past 200 kyr. A calcification index (CI) based on the coccolith weight and length is applied to evaluate the changes in coccolithophore calcification. The two groups of coccolith weights / CIs show different patterns on long term variations and during the last two terminations. We compare the coccolith weight and CI records with the environmental variables and carbonate chemistry parameters calculated in the same core. Our data reveals that sea surface temperature and insolation have weak correlations to coccolith weight and CI on long-term variations. The SPC weight / CI are correlated with the seawater pH and pCO2 variations while the GEO weight/ CI are more related to the nutrient variations. This imply a more significant role of ocean carbonate chemistry in the calcification of less calcified coccolithophores and nutrient concentration in the heavier calcifying coccolighophores.

Continue reading ‘Late Quaternary coccolith weight variations in the northern South China Sea and their environmental controls’

Combination of ocean acidification and warming enhances the competitive advantage of Skeletonema costatum over a green tide alga, Ulva linza

Highlights

• Coculture did not affect growth rate of U. linza but decreased it for S. costatum.

• Elevated CO2 relieved the inhibitory effect of U. linza on growth of S. costatum.

• At elevated CO2, higher temperature increased the growth rate of S. costatum.

• At elevated CO2, higher temperature reduced the growth rate of U. linza.

• Coculture did not affect respiration of U. linza but stimulated it for S. costatum.

Abstract

Red tide and green tide are two common algal blooms that frequently occur in many areas in the global oceans. The algae causing red tide and green tide often interact with each other in costal ecosystems. However, little is known on how future CO2-induced ocean acidification combined with temperature variation would affect the interaction of red and green tides. In this study, we cultured the red tide alga Skeletonema costatum and the green tide alga Ulva linza under ambient (400 ppm) and future CO2 (1000 ppm) levels and three temperatures (12, 18, 24 °C) in both monoculture and coculture systems. Coculture did not affect the growth rate of U. linza but significantly decreased it for S. costatum. Elevated CO2 relieved the inhibitory effect of U. linza on the growth of S. costatum, particularly for higher temperatures. At elevated CO2, higher temperature increased the growth rate of S. costatum but reduced it for U. linza. Coculture with U. linza reduced the net photosynthetic rate of S. costatum, which was relieved by elevated CO2. This pattern was also found in Chl a content, indicating that U. linza may inhibit growth of S. costatum via harming pigment synthesis and thus photosynthesis. In monoculture, higher temperature did not affect respiration rate of S. costatum but increased it in U. linza. Coculture did not affect respiration of U. linza but stimulated it for S. costatum, which was a signal of responding to biotic and/abiotic stress. The increased growth of S. costatum at higher temperature and decreased inhibition of U. linza on S. costatum at elevated CO2 suggest that red tides may have more advantages over green tides in future warmer and CO2-enriched oceans.

Continue reading ‘Combination of ocean acidification and warming enhances the competitive advantage of Skeletonema costatum over a green tide alga, Ulva linza’

Combined effects of CO2-driven ocean acidification and Cd stress in the marine environment: enhanced tolerance of Phaeodactylum tricornutum to Cd exposure

Highlights

• Combined effects of OA and Cd exposure on Phaeodactylum tricornutum were analyzed.

• Either OA (1500 ppm) or Cd stress (1.2 mg/L) alone inhibited the growth of P. tricornutum.

• A significantly enhanced tolerance of P. tricornutum to Cd of 1.2 mg/L occurred under OA.

Abstract

Ocean acidification (OA) and heavy metals are common stress factors for marine ecosystems subject to anthropogenic impacts. OA coupled with the heavy metal is likely to affect marine species. This study investigated the single and combined effects of OA (1500 ppm) and cadmium (Cd; 0.4, 1.2 mg/L) on the marine diatom Phaeodactylum tricornutum under 7 d exposure. The results clearly indicated that either OA or Cd stress (1.2 mg/L) alone inhibited the growth of P. tricornutum. However, under the combined OA-Cd stress, the growth inhibition disappeared, and the intracellular oxidative damage was mitigated. These results indicated a significantly enhanced tolerance of P. tricornutum to Cd while under OA conditions, which could be beneficial to the survival of this diatom. This study will ultimately help us understand the responses of marine organisms to multiple stressors and have broad implications for the potential ecological risks of Cd under future OA conditions.

Continue reading ‘Combined effects of CO2-driven ocean acidification and Cd stress in the marine environment: enhanced tolerance of Phaeodactylum tricornutum to Cd exposure’

A metabolomic approach to investigate effects of ocean acidification on a polar microalga Chlorella sp.

Highlights

• Future ocean acidification levels have little effect on the growth and photosynthesis of Chlorella sp.

• Ocean acidification promoted saturation of fatty acids and amino acid synthesis of Chlorella sp.

• Enhancement of energy production and trehalose synthesis could be the acclimation strategies of marine picochlorophytes.

Abstract

Ocean acidification, due to increased levels of anthropogenic carbon dioxide, is known to affect the physiology and growth of marine phytoplankton, especially in polar regions. However, the effect of acidification or carbonation on cellular metabolism in polar marine phytoplankton still remains an open question. There is some evidence that small chlorophytes may benefit more than other taxa of phytoplankton. To understand further how green polar picoplankton could acclimate to high oceanic CO2, studies were conducted on an Antarctic Chlorella sp. Chlorella sp. maintained its growth rate (∼0.180 d-1), photosynthetic quantum yield (Fv/Fm = ∼0.69) and chlorophyll a (0.145 fg cell-1) and carotenoid (0.06 fg cell-1) contents under high CO2, while maximum rates of electron transport decreased and non-photochemical quenching increased under elevated CO2. GCMS-based metabolomic analysis reveal that this polar Chlorella strain modulated the levels of metabolites associated with energy, amino acid, fatty acid and carbohydrate production, which could favour its survival in an increasingly acidified ocean.

Continue reading ‘A metabolomic approach to investigate effects of ocean acidification on a polar microalga Chlorella sp.’

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 to 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 a long-lasting impact on coastal carbon cycles and the ecosystem. Accordingly, corresponding countermeasures have been proposed in our study for future reference in ecosystem management strategies and sustainable development policy.

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

Effects of increasing temperature and acidification on the growth and competitive success of Alexandrium catenella from the Gulf of Maine

Highlights

• Growth rates of an Alexandrium catenella decrease at future temperature levels.

• Growth rates of co-occurring non-toxic dinoflagellate competitors increase.

• The findings suggest fewer future toxic blooms in the southern Gulf of Maine.

• But more toxic blooms may occur in the northeastern Gulf of Maine.

Abstract

Climate driven increases in ocean temperature and pCO2 have the potential to alter the growth and prevalence of future Harmful Algal Blooms (HABs), but systematic studies on how climate drivers influence toxic algal species relative to non-toxic phytoplankton are lacking. In particular, little is known about how future climate scenarios will affect the growth of the toxic dinoflagellate Alexandrium catenella, which is responsible for the paralytic shellfish poisoning (PSP) events that threaten the health and economy of coastal communities in the Gulf of Maine and elsewhere. The growth responses of A. catenella and two other naturally co-occurring dinoflagellates in the Gulf of Maine—Scrippsiella sp., and Amphidinium carterae—were studied in mono and mixed species cultures. Experimental treatments tested the effects of elevated temperature (20 °C), lower pH (7.8), and the combination of elevated temperature and lower pH on growth rates relative to those in near-current conditions (15 °C; pH 8.1). Growth rates of A. catenella decreased under elevated temperature and lower pH conditions, a response that was largely attributable to the effect of temperature. In contrast, growth rates of Scrippsiella sp. and A. carterae increased under elevated temperature and lower pH conditions, with temperature also being the primary driver of the response. These trends did not change substantially when these species were grown in mixed cultures (A. catenella + Scrippsiella sp., and A. catenella + A. carterae), indicating that allelopathic or competitive interactions did not affect the experimental outcome under the conditions tested. These findings suggest that A. catenella blooms may become less prevalent in the southern regions of the Gulf of Maine, but potentially more prevalent in the northeastern regions of the Gulf of Maine with continued climate change.

Continue reading ‘Effects of increasing temperature and acidification on the growth and competitive success of Alexandrium catenella from the Gulf of Maine’

Coastal dynamic, nitrate (NO3-) phosphate (PO4-) and phytoplankton abundance at Morodemak North Java Sea Indonesia

Coastal dynamic of North Java sea was the influence of the west and east monsoon as well as interseasonal effect during April-June and October-December. Espescialy to coastal current patern and to nitrate and phosphate variation and ultimately to phytoplankton. Study area focused at 110°52’03.72”E – 110°54’68” E and 06°80.4’75”S – 06°82’72.22”S. The study was conducted for 1 mont in September 2014. Location of this research at Morodemak waters of North Java Sea. Aim of study was to built current spatial model, measure insitu nitrate and phosphate variation and phytoplankton abundance. Coastal current spatial modelling was done using SMS-v8.1 and sampling site based to purposive sampling represetative to the estuary and coastal system. Spatial modelling using Arc.GIS 10 software. The study revealed that nitrate concentration ranged at 0.60 – 2.0 mg/l, phosphate 0.04 – 0.24 mg/l and current speed 0.0003 – 0.0033 m/sec to southeast direction. About 22 genera of phytoplankton were found, with moderate dominancy of Baccilariophyceae, Dinophyceae and most dominance of Rhizosolenia. Most abundance of phytoplankton was at the mouth of the river or the estuary with 28,090,000 cell/m3. Lowest abundance at offshore coastal site with 17,060,000 cell/m3. The highest diversity index (H’) was 1.606 at the estuary and the lowest was 0.8730 at coastal offshore.

Continue reading ‘Coastal dynamic, nitrate (NO3-) phosphate (PO4-) and phytoplankton abundance at Morodemak North Java Sea Indonesia’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

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