CICEET Progress Report for the period 8/1/99 through 2/15/00

Project title:

    Identification and Assessment of Anthropogenic Eutrophication in Shallow Estuaries (CICEET-UNH #99-304, NOAA NA87OR0512)

 Principal investigator:

Ivan Valiela
Reporting period
February 2000, second year.

 I. Accomplishments

    Scheduled tasks

    For the second year of our work, we planned to sample the several sites in Waquoit Bay, Apalachicola Bay, and Great Bay. We measured biomass and production of phytoplankton, as well as biomass and growth of macroalgae and seagrasses. In addition, water samples and producers were collected for determination of nitrogen stable isotope signatures in all of the estuaries.
Progress on tasks
In Waquoit Bay we have monthly water column nutrient data, as shown for nitrate in Fig. 1. Water column samples were also analyzed for ammonium and organic nitrogen [data available but not yet compiled]. Chlorophyll data are available [Fig. 2], phytoplankton production also measured, but data are not compiled yet. Macroalgal [Fig. 3], and seagrass [Fig. 4] biomass have been measured in all the sites.
Figure 1. Monthly nitrate (NO3) values for Waquoit Bay National Estuarine Research Reserve estuaries: Childs River (CR), Quashnet River (QR), Sage Lot Pond (SLP), Waquoit Bay (WB), and Vineyard Sound (VS). Superimposed on the WBNERR seasonal NO3 trends are Great Bay National Estuarine Research Reserve estuaries; Lamprey River (LR) and Oyster River (OR) as well as Apalachicola National Estuarine Research Reserve estuaries; Nick’s Hole (NH) and Yent’s Bayou (YB).
Figure 2. Monthly chlorophyll values for Waquoit Bay National Estuarine Research Reserve estuaries: Childs River (CR), Quashnet River (QR), Sage Lot Pond (SLP), Waquoit Bay (WB), and Vineyard Sound (VS). Superimposed on the WBNERR seasonal chlorophyll trends are Great Bay National Estuarine Research Reserve estuaries; Lamprey River (LR) and Oyster River (OR) as well as Apalachicola National Estuarine Research Reserve estuaries; Nick’s Hole (NH) and Yent’s Bayou (YB).
Figure 3. Seasonal macroalgal biomass (g DW m-2) values for Waquoit Bay National Estuarine Research Reserve estuaries: Childs River, Quashnet River, and Sage Lot Pond. Superimposed on the WBNERR seasonal macroalgal biomass are Great Bay National Estuarine Research Reserve estuaries; Lamprey River and Oyster River as well as Apalachicola National Estuarine Research Reserve estuaries; Nick’s Hole and Yent’s Bayou.
Figure 4. Seasonal seagrass biomass (g m-2) values for Sage Lot Pond (Zostera marina), Nick’s Hole and Yent’s Bayou (Halodoule wrightii).


In Great Bay we have sampled the Lamprey and Oyster Rivers during May and August. We measured nutrients [Fig. 1], phytoplankton chlorophyll [Fig. 2] (phytoplankton production also measured, data not yet compiled), as well as macroalgal [Fig. 3] and eelgrass biomass and growth [Fig. 5; Tables in Appendix].
CLICK HERE TO DOWNLOAD THE APPENDIX (MS WORD DOCUMENT)
Figure 5. Leaf biomass and growth (Zostera marina) in Great Bay, NH.
In Apalachicola Bay we sampled Nick’s Hole and Yent’s Bayou during April, June, and September. Data were collected for the same variables as in the other estuaries mentioned above [Figs. 1, 2, 3, 4, 6 and Tables in Appendix].
Figure 6. Comparison of seagrass (Haloduole wrightii) leaf growth (g DW m-2 d-1) in Nick’s Hole and Yent’s Bayou (ANERR) in March and September.


In all sites we collected water and producers for determination of stable isotopes [Table 1]. In systems where the load may be dominated by wastewater the d15N signature are inded heavier [Fig. 7]. The next step is use models to calculate actual loads to each of the systems so that we can graph the signatures versus actual values of load instead of the presumed ranks. Water column samples have been collected for d15N analysis and will be incorporated into the final analysis after we complete processing of the samples and mass spectrometry.
Figure 7. d15N (‰) signature of producers (phytoplankton, seagrasses, and macroalgae) collected in Sage Lot Pond, Lamprey River, Childs River, and Oyster River. Estuaries are ranked along the x-axis according to what the expected N-load might be (from low to high).
Table 1.

 Difficulties encountered

The data in Fig. 1, for example, suggest that to more precisely describe annual patterns and the annual mean concentrations and biomass, we should obtain more data points, at least from Jul-Aug, and one winter point for the sites we have been investigating. Opting to return to the estuaries for more sampling makes it necessary to cut something else out. We believe it is preferable to make an effort for seasonal sampling in any study site rather than sampling a greater number of sites only twice a year. We therefore plan to continue sampling in Waquoit Bay, increase the sampling frequency in Great Bay, Apalachicola Bay, Weeks Bay, and not including Mullica River. We believe this change in plan will answer all the initial questions posed, while providing better data.

Preliminary data

Most of the progress detailed in section B is depicted in Plots 1-7. The tables in the Appendix detail the macrophyte diversity and abundance found in each site on each sampling date.

 

II. Tasks for the next reporting period

Following the rationale explained in section C, we opt to alter our data collection plans in the following way:
  1. Continue work in monthly coverage of Waquoit Bay sites for complete seasonal coverage and assessment of inter-annual differences.
  1. Return to Great Bay and Apalachicola Bay in mid summer (July) and midwinter to complete seasonal coverage to our data. Our results clearly point out the need to do this.
  2. Start seasonal work in Weeks Bay. J. Cebrian will move to a permanent faculty position in Dauphin Is. Sea Lab in Feb., and so he will be near both Weeks Bay and Apalachicola. This will make it far less costly to cover these sites, and to do so seasonally.
  3. We will omit sampling in Mullica for this work. This is a tradeoff: better seasonal coverage in the other sites, at the cost of one less site.
  4. Complete synthesis of data, and start manuscripts on changes in vegetation prompted by changing loading regimes, and on the response of stable isotopic signatures to the differences in watershed mosaics among the different sites.