Temporal Variation of Bacterial Respiration and Growth Efficiency in Tropical Coastal Waters

Abstract

We investigated the temporal variation of bacterial production, respiration, and growth efficiency in the tropical coastal waters of Peninsular Malaysia. We selected five stations including two estuaries and three coastal water stations. The temperature was relatively stable (averaging around 29.5°C), whereas salinity was more variable in the estuaries. We also measured dissolved organic carbon and nitrogen (DOC and DON, respectively) concentrations. DOC generally ranged from 100 to 900 M, whereas DON ranged from 0 to 32 M. Bacterial respiration ranged from 0.5 to 3.2 M O 2 h ؊1 , whereas bacterial production ranged from 0.05 to 0.51 M C h ؊1 . Bacterial growth efficiency was calculated as bacterial production/(bacterial production ؉ respiration), and ranged from 0.02 to 0.40. Multiple correlation analyses revealed that bacterial production was dependent upon primary production (r 2 ‫؍‬ 0.169, df ‫؍‬ 31, and P < 0.02) whereas bacterial respiration was dependent upon both substrate quality (i.e., DOC/DON ratio) (r 2 ‫؍‬ 0.137, df ‫؍‬ 32, and P ‫؍‬ 0.03) and temperature (r 2 ‫؍‬ 0.113, df ‫؍‬ 36, and P ‫؍‬ 0.04). Substrate quality was the most important factor (r 2 ‫؍‬ 0.119, df ‫؍‬ 33, and P ‫؍‬ 0.04) for the regulation of bacterial growth efficiency. Using bacterial growth efficiency values, the average bacterial carbon demand calculated was from 5.30 to 11.28 M C h ؊1 . When the bacterial carbon demand was compared with primary productivity, we found that net heterotrophy was established at only two stations. The ratio of bacterial carbon demand to net primary production correlated significantly with bacterial growth efficiency (r 2 ‫؍‬ 0.341, df ‫؍‬ 35, and P < 0.001). From nonlinear regression analysis, we found that net heterotrophy was established when bacterial growth efficiency was <0.08. Our study showed the extent of net heterotrophy in these waters and illustrated the importance of heterotrophic microbial processes in coastal aquatic food webs.As our understanding of the marine food web evolves, we recognize the importance of microorganisms in aquatic ecosystems. Bacteria are the main respirers and recycle a large pool of dissolved organic matter to higher trophic levels (6, 13). Therefore, bacterial production is a key process in dissolved organic matter flux. However, the transfer of dissolved organic matter to bacteria is more accurately reflected by bacterial carbon demand (BCD) or carbon consumption (23). One way to obtain BCD from bacterial production is through bacterial growth efficiency (BGE) or growth yield. BGE is an important parameter to evaluate the fate of organic carbon inputs and to determine whether bacteria act as a link (recyclers) or sink (mineralizers). Therefore, understanding the patterns of variation in BGE is fundamental for our knowledge of carbon cycling (14).BGE is essentially the ratio of carbon converted to biomass relative to all the carbon consumed, where carbon consumption is either measured as the sum of bacterial production and respiration (5, 24), dissolved organic ...

Temporal variation of phytoplankton growth and grazing loss in the west coast of Peninsular Malaysia

“…higher TSS levels and lower Secchi disc depth). These observations reflected the poorer water quality that prevails at Klang (Lee et al 2009). …”

“…In the classical pathway, phytoplankton production is transferred to higher level via grazing, and subsequently affects fishery yield (Mann 1993) whereas in the microbial pathway, phytoplankton production is coupled to bacterial consumption via the 15 dissolved organic matter pool (Azam et al 1983, del Giorgio et al 1997, Cole 1999. Although the microbial pathway is relatively well-studied in the coastal waters of Peninsular Malaysia (Lee and Bong 2008, Lee et al 2009, Bong and Lee 2011, Lee and Bong 2012, the classical pathway remains poorly characterized.…”

High bacterial carbon demand and low growth efficiency at a tropical hypereutrophic estuary: importance of dissolved organic matter remineralization

“…The high and continuous input of allochthonous nutrients and organic material from the surrounding lands and the domestic sewage leads to high phytoplankton and bacterial growth (BARRERA-ALBA et al, 2008;GAULKE et al, 2010;VALENTIN, 2008b;MORTAZAVI et al;SCHUMANN et al, 2003;YUAN et al, 2010). However, most of estuarine BGE in situ estimates were performed in temperate zones, with few exceptions on the tropics (GUENTHER et al, 2008a;LEE et al, 2009;RAM et al, 2003;RAM et al, 2007).…”

Long-term and short-term variations of Escherichia coli population structure in tropical coastal waters

“…Salinity at Klang also varied over a wider range (Coefficient of Variation, CV = 44 %) relative to Port Dickson (CV = 3 %). DO concentration at Klang (141 ± 52 lM) was also lower than Port Dickson (235 ± 42 lM) (Student's t test: t = 4.58, df = 19, p \ 0.001) and reflected the eutrophic conditions at Klang (Lee and Bong 2008;Lee et al 2009). …”