Phytoplankton growth and microzooplankton grazing rates in a restricted Mediterranean lagoon (Bizerte Lagoon, Tunisia)

Hlaili, Asma Sakka; Grami, Boutheina; Mabrouk, Hassine Hadj; Gosselin, Michel; Hamel, Dominique

doi:10.1007/s00227-006-0522-y

Cited by 50 publications

(25 citation statements)

References 75 publications

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“…The Shannon Weaver index was lower in 2006 with prevailing diatom abundances and the presence of large dinoflagellates. Such high abundances in microphytoplankton under similar conditions were already observed in the Bay of Naples (Ribera d' Alcalà et al 2004) and in an enclosed Mediterranean area in Tunisia (Sakka Hlaili et al 1990). The elevated temperatures suggest a stratification of the surface waters, decreasing nutrient availability that may explain the concentration increase in dinoflagellate and cyanobacteria-type cells.…”

Section: Discussionsupporting

confidence: 50%

Phytoplankton distribution during two contrasted summers in a Mediterranean harbour: combining automated submersible flow cytometry with conventional techniques

Thyssen

Beker

Edi̇ger

et al. 2010

Environ Monit Assess

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Automated in situ flow cytometry, high-pressure liquid chromatography (HPLC), optical microscopy and fluorometry were combined to monitor phytoplankton over two summer periods (2005 and 2006). In 2006, temperature was higher and nutrients lower than in 2005, generating differences in the phytoplankton assemblages (i.e., abundance and structure). Pigment-size classes based on daily HPLC analysis provided evidence for higher proportions of picoplankton and nanoplankton with higher biomass in 2005 and a dominance of microplankton with lower biomass in 2006, the latter with lower specific diversity, as evidenced by weekly microscopy analyses. Total chlorophyll a estimations from fluorometry measurements recorded every 30 min were higher in 2005 than in 2006, as for the HPLC chlorophyll a concentrations. An automated in situ flow cytometer (Thyssen et al., J Plankton Res 30(9):1027-1040, 2008a) sampled seawater every 30 min. Data analysis yielded the resolution of seven clusters based on light scatter and fluorescence. In 2006, an increase in abundance of the largest cells was observed, confirming pigment and microscopy data. The results suggest that the ecosystem was on a constant renewing process in summer 2005 due to a strong wind event and on a highly productive and recycling way in summer 2006 due to stratification of the upper water layer. Automated submersible flow cytometry confirms to be a powerful tool providing high-resolution data by monitoring phytoplankton at the single cell level. This technology gives access to the shape of the light scatter and fluorescence signals generated by each cell passing through a laser beam and that are linked to size, structure and pigment content of the target cell. When combined with conventional techniques, it further improves our understanding of phytoplankton assemblages.

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Section: Discussionsupporting

confidence: 50%

Phytoplankton distribution during two contrasted summers in a Mediterranean harbour: combining automated submersible flow cytometry with conventional techniques

Thyssen

Beker

Edi̇ger

et al. 2010

Environ Monit Assess

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“…Dans ce contexte, les études effectuées par SAKKA-HLAILI et al (2007, 2008) distinguent deux chaînes trophiques différentes dans les secteurs nord et sud de la lagune de Bizerte.…”

Section: Discussionunclassified

Caractérisation hydrobiologique saisonnière de la lagune de bizerte (Tunisie)

Béjaoui

Ferjani

Zaaboub

et al. 2010

rseau

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Cette étude a pour but la caractérisation hydrobiologique d’une lagune méditerranéenne (lagune de Bizerte, nord de la Tunisie) sur la base de dix campagnes de mesures réalisées à une fréquence mensuelle durant l’année 2004, de janvier à décembre. Deux parmi ces dix campagnes ont fait l’objet d’un maillage fin avec 118 stations en mai et 40 stations en septembre. Le reste n’a couvert que 10 stations seulement. Pendant ces campagnes, des paramètres physicochimiques ont été mesurés (Température, Salinité, Oxygène dissous). Des mesures de paramètres chimiques et biologiques ont été effectuées au laboratoire (Ammonium, Nitrates, Phosphates, Azote total, Phosphore total, Chlorophylle a et Phéopigment).Une analyse multivariée des données collectées a permis de distinguer deux principaux modes de fonctionnement de la lagune. Le premier mode, expliquant 26,3 % de la variance totale, montre un contraste nord-sud et reflète l’effet relatif de la Méditerranée et du bassin versant de la lagune, alors que le second mode, expliquant 18,2 % de la variance totale, montre un contraste est-ouest qui traduit l’effet du lac Ichkeul. Les paramètres qui contribuent significativement au premier mode sont la température, la salinité, la transparence absolue et relative. Ceux qui contribuent au second mode sont la transparence absolue et relative ainsi que la chlorophylle a et le phéopigment. Cependant, les paramètres dont les poids moyens sont non significatifs ont montré des oscillations spatiales importantes en fonction des saisons qui sont en liaison avec les rejets terrestres.The purpose of this study was the hydrobiological characterization of a Mediterranean lagoon (Bizerte Lagoon, North Tunisia) based on ten sampling campaigns carried out during the year 2004, from January to December, on a roughly monthly frequency. Two of these ten campaigns were subject to a high spatial coverage with 118 stations in May and 40 stations in September; the eight remaining campaigns covered only ten stations. During these campaigns, physicochemical parameters were measured (temperature, salinity, dissolved oxygen) and laboratory analyses were performed for chemical and biological parameters (ammonium, nitrate, phosphate, total nitrogen, total phosphorus, chlorophyll-a and pheopigments). A multivariate analysis distinguished two principal functioning hydrobiologic modes. The first mode, explaining 26.3% of the total variance, shows a North-South contrast reflecting the relative effect of the Mediterranean Sea and the catchment area. The second mode, explaining 18.2% of the total variance, shows an East-West contrast that reflects the effect of Lake Ichkeul. The parameters that contribute significantly to the first mode are temperature, salinity, absolute and relative transparency, whereas those that contribute to the second mode are absolute and relative transparency as well as chlorophyll-a and pheopigments. However, parameters for which the average weights were not significant showed important spatial oscillations according to seasons, in relatio...

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“…The diversity of microzooplankton in Suisun and Grizzly Bays is very similar to that observed further downstream in San Pablo Bay (Rollwagen- Bollens and Penry 2003;Rollwagen-Bollens et al 2006), and the overall abundance is comparable although somewhat (~5-15%) lower than in other temperate and subtropical estuaries (e.g., Dolan and Coats 1990;Muylaert et al 2000;Sakka Hlaili et al 2007). …”

Section: Discussionmentioning

confidence: 52%

“…In spring of both years, these high microzooplankton grazing rates resulted in microzooplankton consuming as much as 73% of phytoplankton standing stock. Similarly high microzooplankton grazing rates have been observed in a wide range of estuarine (Leising et al 2005;Sakka Hlaili et al 2007;Sime-Ngando et al 1995) and coastal/open ocean environments (Calbet and Landry 2004).…”

Section: Discussionmentioning

confidence: 97%

The Role of Protistan Microzooplankton in the Upper San Francisco Estuary Planktonic Food Web: Source or Sink?

Rollwagen‐Bollens

Gifford²,

Bollens

2011

Estuaries and Coasts

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Decline of native pelagic species in estuarine systems is an increasing problem, especially for native fishes in the San Francisco Estuary and Delta (SFE-D). Addressing these losses depends on understanding trophodynamics in the food web that supports threatened species. We quantified the role of microzooplankton (heterotrophic-mixotrophic protists <200 μm) in the food web of the upper SFE-D. We sampled protist plankton abundance and composition at two sites (Suisun Bay and Grizzly Bay) approximately monthly from February 2004 to August 2005 and conducted dilution experiments during spring and summer of both years in Suisun Bay. Heterotrophs dominated the protist community in Suisun Bay and Grizzly Bay, particularly in the <20 μm size range, and peaks in protistan microzooplankton biomass were associated with high phytoplankton biomass. In both years, microzooplankton grazing rates were high (0.5-0.7 day −1 ) during the spring and lower (~0.2 day −1 ) during summer. Phytoplankton growth rates peaked in April 2004 (~0.7 day −1 ) but were much lower (<0.1 day −1 ) in spring 2005, despite relatively high abundance. Thus, microzooplankton grazing consumed as much as 73% of phytoplankton standing stock during spring and~15% of standing stock during summer of both years. Combined with earlier results, we conclude that microzooplankton can be important mediators of carbon and energy flow in the upper SFE-D and may be a "source" to the metazoan food web.

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Phytoplankton growth and microzooplankton grazing rates in a restricted Mediterranean lagoon (Bizerte Lagoon, Tunisia)

Cited by 50 publications

References 75 publications

Phytoplankton distribution during two contrasted summers in a Mediterranean harbour: combining automated submersible flow cytometry with conventional techniques

Phytoplankton distribution during two contrasted summers in a Mediterranean harbour: combining automated submersible flow cytometry with conventional techniques

Caractérisation hydrobiologique saisonnière de la lagune de bizerte (Tunisie)

The Role of Protistan Microzooplankton in the Upper San Francisco Estuary Planktonic Food Web: Source or Sink?

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