Project Title: Refinement of Bacterial Growth Efficiency as an Index of Salt Marsh Ecological Function
Principal Investigator(s): Roger I. E. Newell, Paul del Giorgio

Accomplishments
Scheduled Tasks:

1. The two restoration marshes, adjacent natural marsh, and open Bay sites in New Jersey will be sampled twice to allow us to follow Bacterial Growth Efficiency (BGE) in the marshes for a further year. This will allow us to document changes in BGE for a total of 6 y as restoration progresses in these marshes. This sampling will also provide information on any possible seasonality in BGE in natural marshes.
   
   
2. Write a technical manual documenting our methodology in sufficient detail that it can be used by others to measure BGE using our procedures.
   
   
3. Contact investigators who have been performing environmental monitoring on plant and animal abundances in the restoration and reference mashes. These data have been collected by various investigators and consultants contracted by PSE&G as part of the permit agreements required by these mitigation projects. Compare these assessments of salt marsh restoration success to our measurement of BGE in the restoration and reference marshes over the 6 y for which we have data.

Progress on Tasks

1. The major objective of our research has been to assess ways to describe salt marsh microbial function and use these approaches to assess tidal marsh deterioration or restoration. We have focused on bacterial growth efficiency (BGE), because it is a parameter that integrates various aspects of bacterial metabolism and is, in turn, affected by a variety of resource factors, such as nutrient and organic matter availability. BGE is tightly coupled to the physiological condition of bacteria, and in this respect may be an extremely sensitive index of the response of aquatic bacteria to their environment. In particular, we hypothesized that tidal marshes differ from adjacent open waters in terms of bacterial metabolism, and further, that marshes undergoing different stages of degradation or restoration should differ from pristine marshes. During this year we carried out two surveys of microbial metabolism in the same marshes which we have been following since 1997. ,The Thompson and Dennis salt marsh sites are in New Jersey have been undergoing restoration since 1997 and we sample them together with adjacent natural marshes and ~ 1 km off shore in Delaware Bay. The spring study was in April and the summer in July.
   
   
2. The methods manual has largely been written and is now being subject to editing and checking
   
   
3. The first contacts to obtain data from other investigators working in these same restoration marshes have been made. We now have agreement for a collaborative publication that will compare our 6 years of BGE data with the data sets collected in the same two restortion an dreferenc emarshes by other investiagtors. These include Ken Strait (PSE&G Technical manager Estuary Enhancement Program) who has information obtained over the same same 6 y time period on the regrowth of natural marsh vegetation and Dr. Ken Able and colleagues (Tuckerton Field station, Rutgers University) who have been routienly measuring fish abundance. We will also include the 2-y data set on bentic invertebrate community compsoition obatined by Dr. GaryTaghon and students working in Dennis Township restoration marshes.

Difficulties Encountered
None.

Anticipated Success in Meeting Project Objectives in Scheduled Project Period
We met the scheduled objectives.

Preliminary Results
One of the main underlying hypotheses of our research was that natural and anthropogenically altered tidal marshes should have differences in microbial metabolism, but that these differences should narrow as restored tidal marshes regain natural ecological and biogeochemical function. The data that we have collected in the past 6 years, some of which has been with the support of CICEET, have confirmed our initial hypothesis and show that indeed bacterial growth efficiency tends to be systematically lower in the marshes that are undergoing restoration compared to the natural Spartina marshes (Figure 1). We had also hypothesized that these differences should tend to narrow in time as the restored marshes regain their natural functions. The long-term data set shows that although there may indeed be a convergence between the values measured in natural and restored mashes, after 6 years of study, restored marshes continue to have consistently lower BGE than contiguous natural marshes (Figure 1). Because bacterial growth efficiency is primarily driven by the availability and quality of nutrients and organic matter, the systematic differences in bacterial growth efficiency suggest profound differences in elemental and organic carbon cycling between natural and altered marshes. This observation is important because other measures of ecosystem function, such as the hydrographic cycle, the development of vascular vegetation and the colonization of the sediments by macrofauna, all quickly converged to show that these restored marshes had essentially regained natural function. Our measures of microbial metabolism, however, suggest that there is at least one important component of marsh function, that still lags behind.

Tasks and activities for next reporting period

Tasks for the next reporting period

1. Complete the writing of the methods manual
   
   
2. Obtain all data from other investigators working in these same restoration marshes.
   
   
3. Compare the patterns that we have measured for BGE during the salt marsh restoration processes with the data obtained from other investigators for other indicators of salt marsh function.
   
   
4. Complete writing for publicatioin in the peer reviwed literure the results from this 4-y project. Two manuscripts have been already completed:

   Apple, J., P. A. del Giorgio and R. I. E. Newell. An experimental estuarine system to assess the response of bacterioplankton communities to anthropogenic nutrient loading. Will be submitted to estuarine, Coastal and Shelf Science in Sept. 2002.

   del Giorgio, P. A. and R. I. E. Newell. The measurements of bacterial growth efficiency in natural bacterioplankton assemblages.

   Three other manuscripts are in an advanced state of preparation:

   del Giorgio, P. A. and R. I. E. Newell. Large-scale patterns in free-living bacterioplankton respiration, production and growth efficiency in tidal marshes and open estuarine waters. Will be submitted to Limnology and Oceanography in October 2002.

   del Giorgio, P. A., D. Tulipani and R. I. E. Newell. An investigation of bacterioplankton respiratory quotients in coastal ecosystems. Will be submitted to Aquatic Microbial Ecology.

   del Giorgio, P. A., and R. I. E. Newell. Long-term trends in microbial metabolism in Spartina marshes after restoration. In preparation for Limnology and Oceanography.

Concerns or difficulties
None.

Expenditures
In no budget categories are expenditures exceeding estimates.