Are Pelagic Diatoms Free from Bacteria?

Direct interactions between phytoplankton and bacteria are hypothesized to impact bloom dynamics, community succession, and primary productivity. Such impacts may be dependent upon bacterial attachment to phytoplankton, but few studies have quantified this relationship in natural marine waters and little is known regarding factors regulating attachment. During a study of thin layer dynamics in Monterey Bay, California, USA, we collected over 18 000 phytoplankton cells and analyzed them for attached bacteria. We focused our statistical analysis on abundant diatoms and dinoflagellates often associated with thin layers and surface slicks. More than 90% of phytoplankton cells analyzed did not harbor attached bacteria. When colonization had occurred, a single attached bacterium was the most common occurrence and few cells had multiple attached bacteria. Visually healthy phytoplankton were rarely colonized, but those collected outside of dense thin layers and surface slicks had higher incidences of colonization and were more likely to harbor multiple bacteria. Longer diatom chains had a higher probability of being colonized and of bacteria being selectively attached to specific regions within the chains. These results strongly suggest that phytoplankton abundance, health, and morphology regulate colonization by bacteria in the natural marine environment.KEY WORDS: Bacteria · Colonization · Attachment · Diatom · Dinoflagellate · Monterey Bay · Thin layers Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 441: [15][16][17][18][19][20][21][22][23][24] 2011 and growing phytoplankton with more colonization occurring when dead diatom cells appeared within the diatom chains (Droop & Elson 1966). Sieburth & Pratt (1975) documented the presence of bacteria attached to phytoplankton and noted that multiple bacteria attached to phytoplankton were rarely observed in their field samples collected from Narragansett Bay, RI, USA. A mesocosm experiment indicated that phytoplankton were heavily colonized by bacteria with attachment increasing at later times in the experiment when chlorophyll a values reached 168 µg l -1 as a result of high nutrient concentrations (Smith et al. 1995). Kaczmarska et al. (2005) found many bacteria attached to old or broken cells of the diatom Pseudo-nitzschia multiseries in cultures, but few were attached to the same diatoms collected from natural assemblages. Species-specific differences may also exist as some species may be more heavily colonized during early stages of growth and some at later stages (Grossart et al. 2006). To date, the timing and extent of attachment and factors regulating this process are poorly understood.In this study we examined the extent of bacterial attachment to diatoms and dinoflagellates in the natural marine environment of Monterey Bay, California, USA. Monterey Bay is a productive marine ecosystem. In spring and early summer, upwelling of nutrient-rich water generates levels of primary productivity that are typical...

Section: Discussionsupporting

confidence: 81%

supporting

confidence: 74%

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

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Bacterial attachment to phytoplankton in the pelagic marine environment

Graff

Rines²,

Donaghay³

2011

“…Most earlier w o r k reported that bacterial growth o n phytoplankton cell surfaces occurs only d u r i n g t h e decomposition p h a s e of phytoplankton blooms (Droop a n d Elson, 1966;Sieburth, 1968; Bell a n d Mitchell, 1972;Bell e t al., 1974) often l e a d i n g to aggregation a n d t h e formation of detrital clumps (Hobbie e t al., 1972; see also Linley a n d Field, 1981). S u b s e q u e n t work suggested that t h e release of extracellular dissolv e d organic matter from living phytoplankton cells m a y also b e of significance as a substrate for t h e growth of microheterotrophic organisms (for reviews s e e Hellebust, 1974).…”

Section: Introductionmentioning

confidence: 99%

Rate of Degradation and Efficiency of Conversion of Phytoplankton Debris by Marine Micro-Organisms

Newell¹,

Lucas²,

Linley³

1981

130

Detritus from the dinoflagellates Scrippsiella (= Peridinurn) trochoidea and Isochrysis galbana and from the diatoms Skeletonema costaturn, Thalassiosira angstii and Chaetoceros tricornuturn incubated at 10 "C in seawater is colonised by a succession of micro-organisms. Primary microbial decomposers in the incubation experiments were bacterial rods and cocci which reached a peak standing stock carbon of 1.86 f 0.76 % of the carbon supplied to the incubation media by the third day of incubation. The bacteria were subsequently replaced by flagellates which attained a mean peak biomass of 12.5 f 3.58 % of the bacterial biomass by Day 6 before declining. Synchronous measurement of the utilisation of dissolved and particulate components from the incubation media shows that there is a well-defined initial sequence of aggregation of particulate matter to form bacterioparticulate complexes, much as have been recorded for natural waters. During this phase, carbon is mainly utilised from the dissolved component of phytoplankton cell debris, whilst the more refractory components including particulate debris is used more slowly. The dissolved organic component comprises a mean of 34 24 % of the total carbon in the debris and has a 50 % utilisation time of only 1.56 d (37.44 h), whereas the particulate component comprises 65 76 % of the total carbon and has a 50 % utilisation time of as much as 11.56 d (277.4 h). Bacterial carbon conversion efficiency (bacterial carbon/detrital carbon used X 100) during the initial phases of colonisation is 9.8 Sb -a value similar to that recorded for bacterial conversion of dissolved components of macrophyte debris. The results suggest that the carbon conversion budget for the decomposition of phytoplankton cell debris is 100 g carbon yielding 4 -644 g of bacterial carbon. This value for incorporation of carbon into bacteria from phytoplankton cell debris is much lower than might be anticipated from the absorption efficiency of selected labile components released in small quantities by living phytoplankton. The carbon conversion budget for whole phytoplankton debris thus suggests that as much as 30.8 % of the carbon is mineralised and returned to the environment within 3 d by the bacteria which initially colonise the material, whereas the more refractory 64.4 %, comprising carbon in the particulate components of the cell debris, is mineralised within approximately 11 d by bacteria characteristically associated with the decomposition phase of a phytoplankton bloom.

“…The bacterial population~ associated with living surfaces, which are an important component in the development of a fouling community (Mitchell & Kirchman 1984), appear to be highly variable. This variability includes epibiotic bacterial densities covering more than 6 orders of magnitude, ranging from organisms with all but sterile surfaces (Droop & Elson 1966, Garland et al 1982, Wahl & Lafargue 1990 to others that exhibit extremely high epibacterial densities (e.g. Sieburth 1975, Novak 1984.…”

Section: Introductionmentioning

confidence: 99%

Chemical control of bacterial epibiosis on ascidians

Wahl¹,

Jensen²,

Fenical³

1994

126

Two CO-occurring ascidians of the Pacific subtidal, Polyclinum planum and Cystodytes lobatus, were found to exhlbit remarkably different numbers of surface bacteria. On average, epibactenal densities on P. planum were 140 times greater than those on C. lobatus as measured by platecounting methods. Organic extracts of both ascidian species were tested for antimicrobial activities and effects on bacterial settlement. Bacterial settlement was measured using a new bioassay described in this paper. The results of the settlement bioassay clearly demonstrate that extracts of the littlecolonized C, lobatus deter bacterial settlement while extracts of the heavily colonized P. planum induce settlement relative to the control. In addition to reduclng bacterial settlement, extracts of C. lobatus colonies exhibited varylng, but generally low, levels of antimicrobial acbvity against, on average, onehalf of the 36 strains of marine bactena tested. On an interspecific level, including 11 ascldian species screened in a pilot study, fouling-deterring activities were correlated with epibacterial abundances while antimicrobial activity was not. It is concluded that the chemical control of bacterial settlement, possibly complemented by antimicrobial toxicity, provides an accurate model to explain the dramatically different bacterial abundance on the surfaces of the ascidian species studied. This investigation presents evidence that non-toxic metabolltes influence bacterial settlement and, in this way, may function to regulate bacterial epibiosis on the surfaces of some marine invertebrates.