Springtime Nutrient and Phytoplankton Dynamics on Georges Bank

The dynamics of phytoplankton and nutrients before, during and after the winter-spring bloom on Georges Bank were studied on 6 monthly survey cruises from January to June 1999. We measured hydrography, phytoplankton cell densities, chlorophyll a, dissolved inorganic nutrients (NO3 + NO2, NH4, Si(OH)(4), PO4), dissolved organic nitrogen (DON) and phosphorus (DOP), particulate organic carbon (POC) and nitrogen (PON) and total particulate phosphorus (TPP). We present evidence that phytoplankton production may be significant year-round, and that the winter-spring bloom may have started in January. From January to April the phytoplankton was comprised almost exclusively of diatoms, reaching cell densities in March and April of ca. 450 cells ml(-1); chlorophyll a concentrations exceeded 10 mug l(-1) in April. Diatoms decreased to relatively low levels in May (< 50 x 10(3) cells l(-1)) and increased again in June (>300 x 10(3) cells l(-1)). Densities of dinoflagellates and nanoflagellates were low (< 10 x 10(3) cells l(-1)) from January to April, and increased in May and June to nearly 300 x 10(3) cells l(-1). Nitrate + nitrite concentrations in January were <3 muM in the shallow, central portion of the bank and decreased steadily each month. Silicate was also <3 muM over an even larger area of the central bank in January and declined to <1.5 muM over most of the Bank in April. The data suggest that silicate depletion, not DIN, contributed to the cessation of the diatom bloom. Regeneration of silicate occurred in May and June, presumably as a result of rising water temperatures in late spring which increased the dissolution rate of diatom frustules from the earlier diatom bloom. Dissolved organic nitrogen may have been utilized at the start of the winter-spring bloom; concentrations were ca, 14 muM in January, dropping to < 6 mug l(-1) in February, after which DON concentrations steadily rose to > 15 mug l(-1) in June. Overall micro-and nanoplankton biomass, measured as POC, PON and TPP, increased over the 6 mo period, as did nutritional quality of that biomass as indicated by declining C:N ratios. Our results suggest there may have been an increase in the heterotrophic component of the plankton in May and June which coincided with a second burst in diatom abundance. We discuss general features of planktonic production and nutrient dynamics with respect to year-round production on the Bank.

Use of Otolith Strontium:Calcium Ratios for Hindcasting Larval Cod Gadus Morhua Distributions Relative to Water Masses on Georges Bank

The concentration ratios of strontium to calcium in laboratory-reared larval cod otoliths are shown to be related to the water temperature (T) at the time of otolith precipitation. This relationship is curvilinear, and is best described by a simple exponential equation of the form (Sr/Ca x 1000 = a exp(-T/b). We show that when Sr/Ca elemental analyses are related to the daily growth increments in the larval otoliths, relative temperature histories of individual field-caught larvae can be reconstructed from the egg stage to the time of capture. We present preliminary examples of how such reconstructed temperature histories of Atlantic cod Gadus morhua larvae, collected on Georges Bank during April and May 1993, may be interpreted in relation to the broad-scale larval distributions and the hydrography of the Bank.

Impacts of Technology Adoption: Comparing Returns to the Farming Sector in Maine under Alternative Technology Regimes

This thesis tests if certain technology choices are associated with a reduction in the proportion of farming activities in the agro-food system in Maine. Goodman, Sorj, and Wilkinson define appropriationism as the replacement of farming sector activities by industrial inputs. Based on the concept of appropriationism, industrial fanning systems using large amounts of synthetic inputs contribute less to fanning than more agrarian systems, like organic fanning. Thus, returns to the farming sector should be greater for organic compared with conventional potato fanning in Maine since organic farming uses fewer industrial inputs. Goodman et. al. define substitutionism as the displacement of farming sector commodities and activities by industrial processes in the marketing sector. Based on the concept of substitutionism, returns to the farming sector should be greater for Lay's Classic®™ potato chips made from natural potatoes compared with Baked Lay's®™ potato crisps manufactured from processed dehydrated potatoes. Returns to the farming sector are defined as returns to the farmer or farm family from farming activities, returns to farm labor, and returns to farmers and farm labor producing inputs used on the farm. Results show absolute returns to the farming sector are less for organic compared to conventional tablestock potato farms in Maine. However as a proportion of farm revenues, large organic farms that market at least 25% of their produce to retail stores or directly to consumers do as well as conventional farms. When comparing returns as a proportion of consumer expenditures, these organic farms do better than conventional farms. Returns to the farming sector are less for organic because of yield penalties, cost of marketing services, and diseconomies of size for organic tablestock potato farms. Expanding acreage and reintegrating livestock with cropping systems may increase returns to the fanning sector. Organic farming demonstrates difficulties in providing marketing services at the farm level. Providing marketing services limits the ability to expand production to capture economies of size. Maine organic potato farmers emphasize non-monetary values such as supporting sustainable agriculture, self-sufficiency, the intrinsic value of work, and close community and family connections. Returns to the farming sector as a proportion of consumer expenditures are about three times greater for Lay's Classic®™ potato chips than for Baked Lay's®™ potato crisps, since the value that farmers receive for potatoes used to produce dehydrated potato flakes in one pound of crisps is about half of the value that farmers receive for potatoes used to make one pound of chips. However, this assumes farmers assign a cost to producing low-grade potatoes for dehydration proportionate to their value. Premium potatoes are used to produce potato chips. Low-grade potatoes are used to produce the dehydrated potato flakes used to make potato crisps. Returns to the farming sector are slightly greater for potato crisps if no costs are allocated to producing low-grade potatoes for dehydration. A shift in consumer preferences from potato chips to crisps may result in a geographical shift of potato production from Maine to the Pacific Northwest assuming no food-grade dehydration facilities are built in Maine.