Quantitative exploration of the contribution of settlement, growth, dispersal and grazing to the accumulation of natural marine biofilms on antifouling and fouling-release coatings

Abstract

The accumulation of microbial biofilms on ships' hulls negatively affects ships' performance and efficiency while also moderating the establishment of even more detrimental hard-fouling communities. However, there is little quantitative information on how the accumulation rate of microbial biofilms is impacted by the balance of the rates of cell settlement, in situ production (ie growth), dispersal to surrounding waters and mortality induced by grazers. These rates were quantified on test panels coated with copper-based antifouling or polymer-based fouling-release coatings by using phospholipids as molecular proxies for microbial biomass. The results confirmed the accepted modes of efficacy of these two types of coatings. In a more extensive set of experiments with only the fouling-release coatings, it was found that seasonally averaged cellular production rates were 1.5 ± 0.5 times greater than settlement and the dispersal rates were 2.7 ± 0.8 greater than grazing. The results of this study quantitatively describe the dynamic balance of processes leading to microbial biofilm accumulation on coatings designed for ships' hulls.

Phospholipid turnover rates suggest that bacterial community growth rates in the open ocean are systematically underestimated

“…Our method of determining phospholipid turnover rates relied on only three measurements: (1) membrane phospholipid concentrations ([PL]; mol P i L −1 ), which were determined using liquid chromatography/mass spectrometry (Popendorf et al ); (2) phospholipid synthesis rates ( 33 P i incorporation, PL ; dpm L −1 h −1 ), which were determined via the incorporation rate of exogenous 33 P‐phosphate tracer into specific classes of phospholipids using short‐term bottle incubations, subsequent lipid extraction, and isolation of individual lipid classes by preparative HPLC (Van Mooy et al ); and (3) phosphate concentrations, which were determined using an established method and yield the specific activity of the 33 P‐phosphate (SA 33P ; mol dpm −1 ) (Karl and Tien ). Then, assuming steady‐state in a similar manner to the calculations of μ from 3 H‐TdR and 3 H‐Leu uptake (Eqs.…”

“…For 33 P‐phosphate ( 33 P i ) uptake into phospholipids, 50–200 mL seawater samples were placed in polypropylene centrifuge tubes or acid‐cleaned polycarbonate bottles, spiked with (Perkin Elmer), and incubated in the dark at ambient seawater temperature for 0.5–10 h. Radiolabeled phosphate additions resulted in increases in the total phosphate concentration of less than 0.04 nmol L −1 , and thus did not represent an appreciable nutrient amendment. Lipids were extracted as described above, and phospholipid classes were then separated and purified from the total lipid extract using preparative high performance liquid chromatography (HPLC) as previously described (Van Mooy et al ). The 33 P radioactivity of these phospholipid fractions were then determined by liquid scintillation counting.…”

“…Through advances in geochemical and microbial analytical techniques, multiple lines of evidence now show that two classes of phospholipids, phosphatidylglycerol (PG), and phosphatidylethanolamine (PE) are derived primarily from heterotrophic bacteria in the open ocean, opening the door for using these molecules to evaluate bacterial community growth dynamics (Van Mooy et al 2009;Van Mooy and Fredricks 2010;Popendorf et al 2011;Kharbush et al 2016;Meador et al 2017). We combined previously published approaches to determine biosynthesis rates (Van Mooy et al 2014) and concentrations (Popendorf et al 2013) of PG and PE to calculate the steady-state turnover rates of these molecules. We then explored the relationships between these phospholipid turnover rates and growth rates of heterotrophic bacteria.…”

Long-term microfouling on commercial biocidal fouling control coatings

“…The unique physicochemical properties of biocidal coatings affect the formation of microbial biofilms (Whitehead & Verran 2009;Van Mooy et al 2014). The development of such biofilms in turn depends on the types of microbes present and environmental conditions (Yebra et al 2006b).…”

Variable phosphorus uptake rates and allocation across microbial groups in the oligotrophic Gulf of Mexico

“…Immediately after sorting, lipids were extracted using a modified Bligh and Dyer solvent extraction protocol following Van Mooy and Fredricks (). Following methods described by Van Mooy and colleagues (), three phospholipid headgroup classes of intact polar diacylglycerolipids were then purified from the total lipid extract using preparative high‐pressure liquid chromatography (HPLC): PG, PE and PC. Separation and collection of purified fractions were carried out using an Agilent HP1050 HPLC coupled with a Teledyne ISCO Foxy Jr. fraction collector and normal phase chromatography with a PrincetonSpher diol column (100 Å poresize, 5 μm silica beads, 150 mm × 2.1 mm).…”