Direct and indirect effects of grazing on the phytoplankton seasonal succession in an oligotrophic lake

Carrillo, Presentación; Reche, Isabel; Castillo, Pedro Miguel Sánchez; Cruz-Pizarro, L.

doi:10.1093/plankt/17.6.1363

Cited by 46 publications

(42 citation statements)

References 34 publications

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“…Thus, the interannual patterns in the ratio of total autotrophic to heterotrophic biomass observed in this study provide a good measure of changes in food web structure, suggesting a systematic shift from a complex food web with a well-developed grazing and microbial food web in 1995 to a microbial-dominated food web, where protists were especially important, in 1996. Ciliates and heterotrophic nanoflagellates, organisms rarely found in the lake before this study (Echevarría et al 1990, Carrillo et al 1995, were common during 1995 and 1996. In contrast, larger zooplankton became very scarce in 1996 after the massive input of water associated with snow and ice melt.…”

Section: Changes In Trophic Food Webmentioning

confidence: 74%

“…In contrast, larger zooplankton became very scarce in 1996 after the massive input of water associated with snow and ice melt. The return to normal zooplankton densities for this lake (Carrillo et al 1995) did not occur until the mid-ice-free season (August) of 1997, probably due to the low growth rates of the dominant calanoid copepod ) and the low water temperatures of the lake during the wet years (1996, 1997). In August 1997 the A:H ratio dropped below 1, accounting for the well-documented high herbivore versus autotroph biomass in oligotrophic waters (Gasol et al 1997), and a classical grazing food web was reestablished.…”

Section: Changes In Trophic Food Webmentioning

confidence: 89%

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Microbial plankton response to contrasting climatic conditions: insights from community structure, productivity and fraction stoichiometry

Villar‐Argaiz

Medina‐Sánchez²,

Carrillo³

2002

Aquat. Microb. Ecol.

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Climatic events are among the most important forces governing natural processes in ecosystems. Over a 3 yr period, we monitored changes in the hydrological, chemical and biological regimes of a high mountain lake severely affected by a drought that peaked in 1995. During the drought, the decrease in lake volume enhanced the contribution of the sediment to the lake nutrient budget. The community became more complex, with the appearance of ciliates and heterotrophic nanoflagellates, organisms rarely found prior to the drought. The impaired post-drought recovery of the zooplankton, which did not reach normal densities for this lake until 1997, resulted in a microbialdominated food web in 1996 and a classical grazing food web in 1997. Besides the species composition or abundance and the autotrophic to heterotrophic ratio, food web changes associated with the drought and atmospheric nutrient inputs were reflected in the stoichiometry and contribution of both bacteria and phytoplankton fractions to the planktonic particulate matter. Specific productivity measurements showed that cellular N:P ratios could be used to evaluate the growth conditions of phytoplankton but not of bacteria, indicating that an element other than P may limit bacteria growth. Assessments of phytoplankton and bacteria productivity and of the photosynthetic carbon release relative to bacteria demand in microcosms revealed that after a phosphorus pulse, the phytoplankton N:P ratio determines the nature of the interaction between phytoplankton and bacteria as either commensalistic or competitive for inorganic P. If phytoplankton N:P is initially high (P-deficient algae), a P pulse can reduce photosynthetic extracellular release (PER) and bacteria can experience C limitation, whereas if phytoplankton N:P is initially low (P-sufficient algae) and bacteria N:P is high, increased PER is observed and competition for inorganic P may occur. KEY WORDS: Drought · Atmospheric depositions · Food web · Phytoplankton vs bacteria interaction · Productivity · Stoichiometry Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 29: [253][254][255][256][257][258][259][260][261][262][263][264][265][266] 2002 outlets, where most of the water is exchanged as a result of meteorological processes. Droughts represent extreme conditions of rainfall and temperature that have drastic effects on ecosystems. The fact that climatic models for Europe predict more frequent and intense droughts at lower latitudes (Houghton et al. 1996) means that further experimental research is urgently required on the effects of climate on plankton production and dynamics in aquatic ecosystems.The biological structure of ecosystems serves as an appropriate marker of the strength of the controls operating in planktonic food webs. Thus, it is commonly accepted that phytoplankton dominate the food base in the more productive eutrophic lakes, whereas heterotrophic biomass dominates in less productive lakes (del Giorgio & Gasol 1995, Biddanda et a...

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Section: Changes In Trophic Food Webmentioning

confidence: 74%

Section: Changes In Trophic Food Webmentioning

confidence: 89%

Microbial plankton response to contrasting climatic conditions: insights from community structure, productivity and fraction stoichiometry

Villar‐Argaiz

Medina‐Sánchez²,

Carrillo³

2002

Aquat. Microb. Ecol.

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“…Phytoplankton biovolumes were estimated from measurements of 20-30 cells of each species using image analysis (inverted microscope Axio Observer A1, Zeiss; highresolution microscopy camera Axiocam HRc, Zeiss). Cell volume was calculated according to Carrillo et al (1995), and converted to phytoplankton carbon using the conversion factors reported by Rocha and Duncan (1985). Bacterial abundance (BA) was determined by the 4 ,6-diamidino-2-phenylindole (DAPI) direct-count method described by Porter and Feig (1980).…”

Section: Analysis Biological Variablesmentioning

confidence: 99%

Synergistic effects of UVR and simulated stratification on commensalistic phytoplankton–bacteria relationship in two optically contrasting oligotrophic Mediterranean lakes

et al. 2015

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Abstract. An indirect effect of global warming is a reduction in the depth of the upper mixed layer (UML) causing organisms to be exposed to higher levels of ultraviolet (UVR, 280-400 nm) and photosynthetically active radiation (PAR, 400-700 nm). This can affect primary and bacterial production as well as the commensalistic phytoplankton-bacteria relationship. The combined effects of UVR and reduction in the depth of the UML were assessed on variables related to the metabolism of phytoplankton and bacteria, during in situ experiments performed with natural pico-and nanoplankton communities from two oligotrophic lakes with contrasting UVR transparency (high-UVR versus low-UVR waters) of southern Spain. The negative UVR effects on epilimnetic primary production (PP) and on heterotrophic bacterial production (HBP), intensified under increased stratification, were higher in the low-UVR than in the high-UVR lake, and stronger on the phytoplanktonic than on the heterotrophic bacterial communities. Under UVR and increased stratification, the commensalistic phytoplankton-bacteria relationship was strengthened in the high-UVR lake where excretion of organic carbon (EOC) rates exceeded the bacterial carbon demand (BCD; i.e., BCD : EOC(%) ratio < 100). This did not occur in the low-UVR lake (i.e., BCD : EOC(%) ratio > 100). The greater UVR damage to phytoplankton and bacteria and the weakening of their commensalistic interaction found in the low-UVR lake indicates that these ecosystems would be especially vulnerable to UVR and increased stratification as stressors related to global climate change. Thus, our findings may have important implications for the carbon cycle in oligotrophic lakes of the Mediterranean region.

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“…A variable amount of sample (50-100 mL) was allowed to settle for 48 h in Utermöhl chambers (Hydro-Bios GmbH, Germany) and species were enumerated and identified using an inverted microscope (Leitz Fluovert FS, Leica, Wetzlar, Germany) following the technique described by Villafañe and Reid (1995). Phytoplankton biovolumes were estimated from measurements of 20-30 cells of each species using image analysis (Inverted microscope Axio Observer A1, Zeiss -High resolution microscopy camera Axiocam HRc, Zeiss); biovolumes were calculated according to Carrillo et al (1995). Cell volume was converted to phytoplankton carbon using the conversion factors reported by Rocha and Duncan (1985).…”

Section: Analyses and Measurementsmentioning

confidence: 99%

Interactive effects of vertical mixing, nutrients and ultraviolet radiation: in situ photosynthetic responses of phytoplankton from high mountain lakes in Southern Europe

et al. 2013

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Abstract. Global change, together with human activities, has resulted in increasing amounts of organic material (including nutrients) that water bodies receive. This input further attenuates the penetration of solar radiation, leading to the view that opaque lakes are more "protected" from solar ultraviolet radiation (UVR) than clear ones. Vertical mixing, however, complicates this view as cells are exposed to fluctuating radiation regimes, for which the effects have, in general, been neglected. Furthermore, the combined impacts of mixing, together with those of UVR and nutrient inputs are virtually unknown. In this study, we carried out complex in situ experiments in three high mountain lakes of Spain (Lake Enol in the National Park Picos de Europa, Asturias, and lakes Las Yeguas and La Caldera in the National Park Sierra Nevada, Granada), used as model ecosystems to evaluate the joint impact of these climate change variables. The main goal of this study was to address the question of how short-term pulses of nutrient inputs, together with vertical mixing and increased UVR fluxes modify the photosynthetic responses of phytoplankton. The experimentation consisted in all possible combinations of the following treatments: (a) solar radiation: UVR &plus; PAR (280–700 nm) versus PAR (photosynthetically active radiation) alone (400–700 nm); (b) nutrient addition (phosphorus (P) and nitrogen (N)): ambient versus addition (P to reach to a final concentration of 30 μg P L−1, and N to reach N:P molar ratio of 31); and (c) mixing: mixed (one rotation from surface to 3 m depth (speed of 1 m 4 min−1, total of 10 cycles)) versus static. Our findings suggest that under ambient nutrient conditions there is a synergistic effect between vertical mixing and UVR, increasing phytoplankton photosynthetic inhibition and excretion of organic carbon (EOC) from opaque lakes as compared to algae that received constant mean irradiance within the epilimnion. The opposite occurs in clear lakes where antagonistic effects were determined, with mixing partially counteracting the negative effects of UVR. Nutrient input, mimicking atmospheric pulses from Saharan dust, reversed this effect and clear lakes became more inhibited during mixing, while opaque lakes benefited from the fluctuating irradiance regime. These climate change related scenarios of nutrient input and increased mixing, would not only affect photosynthesis and production in lakes, but might also further influence the microbial loop and trophic interactions via enhanced EOC under fluctuating UVR exposure.

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Direct and indirect effects of grazing on the phytoplankton seasonal succession in an oligotrophic lake

Cited by 46 publications

References 34 publications

Microbial plankton response to contrasting climatic conditions: insights from community structure, productivity and fraction stoichiometry

Microbial plankton response to contrasting climatic conditions: insights from community structure, productivity and fraction stoichiometry

Synergistic effects of UVR and simulated stratification on commensalistic phytoplankton–bacteria relationship in two optically contrasting oligotrophic Mediterranean lakes

Interactive effects of vertical mixing, nutrients and ultraviolet radiation: in situ photosynthetic responses of phytoplankton from high mountain lakes in Southern Europe

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