Maryland Sea Grant

This paper presents evidence of a seasonal shift from P to N as the nutrient limiting the accumulation of algal biomass in Chesapeake Bay. Following the winter/spring maximum in freshwater runoff, (1) the ratio of dissolved inorganic nitrogen to soluble reactive phosphorus (DIN/PO,) was greater than the N/P of algal biomass; (2) alkaline phosphatase activity was high; (3) phosphate turnover times were short; (4) ammonium turnover times were long; and (5) growth rates of phytoplankton were stimulated by additions of phosphate but not by additions of ammonium or silicate. During the period of low runoff in summer, all indicators reversed, and N limited algal growth rates. Silicate concentrations also showed evidence of biological depletion in spring, which may have limited diatom abundance. Due to the concordance of all indicators at large and small scales, we argue that phytoplankton growth rates exert primary control over biomass accumulation. We conclude that P and Si limit the accumulation of algal biomass along the major axis of Chesapeake Bay in spring, whereas N limits algal accumulation in summer, similar to the conclusions of D' Elia et al. (1986; Can. J. Fish. Aquat. Sci. 43: 397-406) for the Patuxent subestuary. Controlling eutrophication of the Bay and its subestuaries will require basin-specific management practices for both N and P reductions in influent waters. Such management efforts will provlde ecosystem tests of nutrient hmitation on a scale similar to those successfully conducted in lakes.

Aquaponics, a combination of fish farming and soilless plant farming, is growing in popularity and gaining attention as an important and potentially more sustainable method of food production. The aim of this study was to document and analyze the production methods, experiences, motivations, and demographics of aquaponics practitioners in the United States (US) and internationally. The survey was distributed online using a chain sampling method that relied on referrals from initial respondents, with 809 respondents meeting the inclusion criteria. The majority of respondents were from the US (80%), male (78%), and had at least a high school degree (91%). The mean age of respondents was 47±13 years old. Most respondents (52%) had three years or less of aquaponics experience. Respondents typically raised tilapia or ornamental fish and a variety of leafy green vegetables, herbs, and fruiting crops. Respondents were most often motivated to become involved in aquaponics to grow their own food, for environmental sustainability reasons, and for personal health reasons. Many respondents employed more than one method to raise crops, and used alternative or environmentally sustainable sources of energy, water, and fish feed. In general, our findings suggest that aquaponics is a dynamic and rapidly growing field with participants who are actively experimenting with and adopting new technologies. Additional research and outreach is needed to evaluate and communicate best practices within the field. This survey is the first large-scale effort to track aquaponics in the US and provides information that can better inform policy, research, and education efforts regarding aquaponics as it matures and possibly evolves into a mainstream form of agriculture.

This paper synthesizes >40 yr of data on phytoplankton abundance in the Chesapeake Bay, USA, spanning the period 1950 to 1990. Long-term changes in the concentrations of surface chlorophyll (B, mg m-3) and integrated water-column chlorophyll (B',,, mg m-2) are assessed in the context of light and nutrient effects on phytoplankton distributions. Significant long-term increases in B were detected from the 1950s to the 1970s in all regions of the Bay. The seaward, polyhaline Bay showed increases in B of 300 to 500%, while mesohaline and oligohaline values increased by between 40 and nearly 400%. Annual means for recent years, 1985-90, showed interannual variations of ca 80%, but trends of the magnitude observed for 1950-70 were not detected. Frequency distributions of B showed shifts in overall distributions to higher values, particularly in the lower, polyhaline Bay where the frequency of B < 2 mg m-3 in the 1950s and 1960s was much higher than in 1985-90. B' ,,, data showed the apparent lack of a winter-spring maximum of contemporary proportions in the 1960s, in contrast to data from the 1970s, early 1980s and 1985-90 that show a well-developed peak in B',,, for most of these years. Nutrient concentrations and ratios have also changed significantly since the 1960s. Concentrations of dissolved inorganic nitrogen (DIN) in the oligohaline Bay have approximately doubled in the past 20 to 30 yr, w M e orthophosphate (Pod3-) concentrations have generally declined, producing a change in DIN: POA3-with rarmfications for nutrient limitation in the Bay. These results are discussed in the context of the regulation of interannual variations m the timing, position and magnitude of the winter-spring phytoplankton bloom in the Bay by freshwater flow from the Susquehanna River.

An analysis of historical and recent data on chlorophyll a for Chesapeake Bay reveals that a significant increase of phytoplankton biomass has occurred during the last 40 to 50 yr. Concentrations of chlorophyll a in the surface mixing layer have increased 5-to 10-fold in the seaward regions of the estuary and 1.5-to 2-fold elsewhere, paralleling published estimates of increased loading of N and P to the estuary since World War 11. The characteristic hlgh vanability of freshwater flow that occurs on seasonal to interannual time scales, however, drives fluctuations of chlorophyll a that are superimposed on this apparent upward trend, potentially obscuring the effects of overenrichment on chlorophyll a concentrations in nutrient-limited regions of the Bay To resolve a time trend of chlorophyll from this variability, we developed regional models of mean, monthly chlorophyll a using autoregressive moving average (ARMA) procedures. The models were developed with water quality data from monitoring cruises of the Chesapeake Bay Program spanning 1984 to 1992. The approach was to: (1) determine the relationship of prominent variables, including freshwater flow, salinity, temperature, region, and time of year, to chlorophyll a for the 'modern' Bay; (2) predict chlorophyll a for the 'historical' Bay based on these models and actual, observed variables for periods from 1950 to 1984 for which chlorophyll a data were available; (3) compare chlorophyll a predicted from modern relationships, to those observed in the past, using the residuals to identify deviations below or above expected concentrations that would suggest a n effect o n chlorophyll a unrelated to flow variability. The results show that: (1) observed and predicted chlorophyll a concentrations matched reasonably well for the years that were used to develop the models, with some exceptions when the models failed to capture extremely high concentrations of chlorophyll a during blooms; (2) chlorophyll a concentrations in the 1950% 1960s and 1970s were predominantly lower than predicted by the models, particularly in the mesohaline and polyhaline regions of the estuary that are most susceptible to nutrient limitation; (3) chlorophyll a concentrations were lower in the 1960s than in the 1970s probably as the result of low flow and a concomitant reduction of nutrient loading in the 'dry' 1960s as compared to the 'wet' 1970s; (4) interannual variability was high for both observed and predicted chlorophyll a concentrations in the 1970% and this variability was most strongly expressed in the mesohaline to polyhaline Bay, reflecting the spatial and temporal heterogeneity of phytoplankton that prevailed in that period. These findings support the hypothesis that a significant increase of chlorophyll a has occurred in the lower Bay that cannot be accounted for by variability of freshwater flow and attendant properties.

Abstract Government agencies in urbanizing areas are increasingly utilizing purchase and transfer of development rights programs to preserve farmland and protect local farm economies. This article tests the effect of development restrictions imposed by permanent easement sales on farmland sales prices, using Maryland data. We correct for selectivity bias due to the voluntary nature of these programs in estimating hedonic sales equations. Although preserved parcels' actual land values are lower, the effect of the restrictions is not statistically significant. These findings may encourage additional participation in preservation programs or justify reductions in the easement prices paid by agencies.

Submonthly variations in warm‐season (January–February) precipitation over South America, in particular over the Amazon basin, central southwest Brazil, north Argentina, and Paraguay are studied. Two distinct regimes of lower tropospheric winds (westerlies and easterlies) were observed in Rondonia during the Wet Season Atmospheric Mesoscale Campaign (WETAMC) component of the Large‐Scale Atmosphere‐Biosphere Experiment in Amazonia (LBA) and the Tropical Rainfall Measuring Mission (TRMM) field campaign. The westerly (easterly) winds were associated with strong (weak) convective activity over the South Atlantic Convergence Zone (SACZ). The period of this study (January and February of 1999) was divided into SACZ and no SACZ (NSACZ) regimes. The vertically integrated moisture fluxes over South America obtained from the National Aeronautics and Space Administration/Goddard Data Assimilation Office (NASA/DAO) assimilation system show that during the SACZ (NSACZ) period, strong (weak) convergence occurred over the Amazon basin with divergence (convergence) over southwestern Brazil, northern Argentina, and Paraguay. These moisture budgets also indicated that moisture transport from the tropics to the extratropics in the South American sector occurs more efficiently during the SACZ regime than during the NSACZ regime.

In hybrid striped bass aquaculture ponds, dinoflagellate blooms were found on 10 of 14 occasions to co-occur with concentrations of urea in excess of 1.5 microM nitrogen. When urea levels were <1.5 microM nitrogen, on seven occasions, no evidence of dinoflagellate blooms was observed in these ponds.

Our purpose was to describe the hypoplastic or plexiform inferior petrosal sinus as a potential cause of false-negative sampling results in patients with Cushing's disease. Five hundred and one patients with surgically proven Cushing's disease and negative or equivocal magnetic resonance imaging scans of the pituitary gland underwent petrosal sinus sampling. Four patients (0.8%) with surgically proven Cushing's disease had false-negative results of petrosal sinus sampling. Retrograde inferior petrosal sinograms in these patients were reviewed to evaluate the anatomy of the inferior petrosal sinuses for abnormalities that could have contributed to this misdiagnosis. In addition, the retrograde inferior petrosal sinograms of 100 consecutive patients were reviewed to establish the frequency of asymmetric and/or hypoplastic inferior petrosal sinuses. All four patients with false-negative results of petrosal sampling demonstrated a hypoplastic or plexiform inferior petrosal sinus ipsilateral to an ACTH-secreting microadenoma. When the sampling catheter was in the hypoplastic petrosal sinus, retrograde sinograms from the contralateral side demonstrated anomalous drainage patterns on the side of the hypoplastic sinus. Because the negative results of petrosal sinus sampling false-suggested the presence of the ectopic ACTH syndrome, curative transsphenoidal surgery in these four patients was delayed up to 31 months. We conclude that the presence of a unilateral hypoplastic or plexiform inferior petrosal sinus can result in anomalous drainage from the pituitary gland that may lead to false-negative sampling results in patients with Cushing's disease.

A century-long decline of the fishery for the Eastern oyster Crassostrea virginica (Gmelin, 1791) in Maryland and Virginia stimulated numerous efforts by federal, state, and nongovernmental agencies to restore oyster populations, with limited success. To learn from recent efforts, we analyzed records of restoration and monitoring activities undertaken between 1990 and 2007 by 12 such agencies. Of the 1,037 oyster bars (reefs, beds, or grounds) for which we obtained data, 43% experienced both restoration and monitoring, with the remaining experiencing either restoration or monitoring only. Restoration activities involved adding substrate (shell), transplanting hatchery or wild seed (juvenile oysters), bar cleaning, and bagless dredging. Of these, substrate addition and transplanting seed were common actions, with bar cleaning and bagless dredging relatively uncommon. Limited monitoring efforts, a lack of replicated postrestoration sampling, and the effects of harvest on some restored bars hinders evaluations of the effectiveness of restoration activities. Future restoration activities should have clearly articulated objectives and be coordinated among agencies and across bars, which should also be off limits to fishing. To evaluate restoration efforts, experimental designs should include replication, quantitative sampling, and robust sample sizes, supplemented by pre- and postrestoration monitoring.

Abstract County level farmland and residential housing values are estimated for the Mid‐Atlantic region as a function of farm returns, developed land values, household incomes, population densities, and location. Results are based on the hypothesis that farmland owners anticipate land development and that nonfarm factors are important determinants of farmland prices. Response of farmland prices to change in farm returns is found to be inelastic and relatively uniform in rural and urban counties. Response to nonfarm factors is found to be more elastic and substantially greater in rural counties.

The winterkpring bloom of 1990 in Chesapeake Bay. USA, was prolonged and well developed, relative to other recent years, along the axis of the Bay. However, the bloom did not occur uniformly along the axis of the Bay, but rather developed and dissipated at different times in different regions of the Bay. The peak of the bloom progressed northward and was observed in late March in South Bay, early April in Mid Bay, and not until mid May in North Bay. We measured biomass and nutrient concentrations and the rates of carbon, nitrogen, phosphorus, and silicon utilization during the development and dissipation of the bloom, and compared ratios of these rates to the elemental ratios of the incoming nutrients and the resulting particulate material. In North Bay, bloom development was probably delayed due to light limitation of carbon uptake. Nitrogen was delivered and utilized in excess of stoichiometric proportions in the northern part of the Bay, eventually leading to phosphorus and/or silicon limitation. In the mid portion of the Bay, the mean stoichiometric proportions of the particulate nutrients were similar to Redfield proportions, but ratios of uptake of nitrogen and phosphorus exceeded Redfield proportions by more than 20-fold, reflecting both the high uptake rates of nitrogen and low uptake rates of phosphorus in that region. However, only at the peak of the bloom in mid April did transient phosphorus limitation of growth occur at Mid Bay. In contrast, ratios of nitrogen to phosphorus uptake rates in South Bay were considerably below Redfield proportions, primarily due to the low availability and low uptake rates of nitrogen. Concentrations of Si(OH), in South Bay were also extremely low through the bloom period, and thus Si(OH), and nitrogen, as well as pod3-, limited growth there. In addition, temperature appeared to play a key role in the collapse of the diatom assemblage in mid May. During the early stages of the bloom in South Bay, No3-+ NOzcontributed >60% of the total nitrogen utilized, but by the end of the spring bloom period in May, over 50% of the nitrogen uthzed was urea alone. These data underscore the need to understand how freshwater flow, ambient nutrient concentrations, temperature, and light dlffer along the axis of the Bay to understand the differential timing and magnitude of bloom development in different regions of the Bay.

ABSTRACT: The Soil Conservation Service (SCS) models, including the TR‐20 computer program and the simplified methods in TR‐55, are widely used in hydrologic design. The runoff curve number (CN), which is an important input parameter to SCS models, is defined in terms of land use tretments, hydrologic, condition, antecedent soil moisture, and soil type. The objective of this study was to evaluate the sensitivity of the SCS models to errors in CN estimates. The results show that the effects of CN variation decrease as the design rainfall depth increases, such as for the larger storm events. The value and use of the sensitivity curves are demonstrated using a comparison of Landsat and conventionally derived curve numbers for three watersheds in Pennsylvania.

The central and eastern equatorial Pacific region is characterized by lower than expected phytoplankton biomass and primary production given the relatively high ambient nitrate concentrations. These unusual conditions have spawned several field programs and laboratory experiments to determine why this high nitrate‐low chlorophyll pattern persists in this region. To synthesize the results from these field programs, as well as providing additional evidence in support of the iron hypothesis, we developed a one‐dimensional, nine‐component ecosystem model of 0°N 140°W. The model components include two phytoplankton size fractions, two zooplankton size fractions, two detrital size fractions, dissolved iron, nitrate, and ammonium. The model was run for 5 years (1990–1994) and was forced using an atmospheric radiative transfer model, an ocean general circulation model (GCM), and in situ data. To our knowledge, this is the first ecosystem model at 0°N 140°W to synthesize the Joint Global Ocean Flux Study Equatorial Pacific Process Study (JGOFS EqPac) data set, as well as to use both in situ and modeled physical data to drive the model. Modeled phytoplankton, zooplankton, and iron all varied on interannual timescales due to El Niño events. Total phytoplankton biomass increased by as much as 40% from early 1992 (El Niño warm) to 1993 (normal). The results also indicate that the biomass increase during a cool period is not constant for each phytoplankton component, but instead the increase is most evident in the netphytoplankton (&gt;10 μm). Netphytoplankton increase from a low of 0.1% of the total chlorophyll in 1992 to a high of 30% of the total in 1993. Microzooplankton grazing rates fluctuated in response to changes in nanophytoplankton growth rates, whereas mesozooplankton grazing was unrelated to netphytoplankton growth rates. The magnitude and temporal variability of phytoplankton chlorophyll agreed well with in situ data collected during 1992. Modeled primary production was lower than measured during El Niño but agreed with observations during normal conditions. The low primary productivity was probably a result of downwelling produced by the physical model. New production was calculated from total and recycled iron rather than nitrate‐based production and was more variable in general and almost 3 times the nitrate‐based new production during non‐El Niño conditions.

Proliferative kidney disease (PKD), caused by an unclassified protozoan (PKX), is reported from Pacific salmon, Oncorhynchus tshawytscha (Walbaum) and O. kisutch (Walbaum), and steelhead trout, Salmo gairdneri Richardson, held at the Mad River Hatchery in California, USA. The cumulative mortality attributed to the disease was 95, 13, and 18% respectively. The mortalities were greatest at mean water temperatures of 12-14 degrees C during July 1983. The ultrastructure of the PKX organism and its associated pathology during clinical disease in all three species were consistent with those of the parasite in rainbow trout (Salmo gairdneri) as described in European outbreaks. Significant mortalities did not occur after August, at which time the parasite could no longer be detected in the salmon species. The steelhead continued to exhibit parasites in the kidney interstitium and epithelium and lumens of the tubules. Myxosporidan trophozoites and developing spores were also observed in the lumens of the kidney tubules of these fish. Although a mixed infection with another parasite may have occurred, evidence suggests that the myxosporidans are later stages of PKX. They were only observed in fish exposed to water with the infective stage and were particularly prominent in recovering fish. The PKX organism is similar to UBO, an unclassified protozoan of carp suspected to be an early stage of Sphaerospora renicola Dykovà & Lom. Both parasites infect the blood and kidney, divide by endogeny, and are released by disintegration of the primary mother cell. The intraluminal myxosporean forms show similarities to Sphaerospora spp. in that they are monosporous and sporoblasts are formed within pseudoplasmodia.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic engineering applied to the production of fish, molluscs, algae, algal products, and crustaceans in natural environments and hatchery systems is still at the rudimentary stage. Cloning systems for producing commercially important chemicals, pharmacologically active compounds, and metamorphosis-stimulating substances present in marine organisms are being sought. Attempts are being made to develop useful drugs from the sea, including antineoplastic, antibiotic, growth-promoting (or -inhibiting), analgesic, and antispasmodic agents. Immediate commercial applications can be expected from engineered systems involving polysaccharide and specialty chemical production, with marine microorganisms as the source of genetic material.

Abstract Two Coastal Plain soils were used to evaluate the effects of organic matter and Fe and Mn hydrous oxides on Zn phytotoxicity, and on Zn, Cd, and Mn uptake by soybean seedlings. Fertilized Pocomoke sl and Sassafras sl were limed to pH 5.5 and 6.3 with CaCO 3 when adding Zn (six levels between 1.3 and 196 mg/kg at pH 5.5; seven levels between 1.3 and 524 mg/kg at pH 6.3). Cadmium was added at 1% of the added Zn. ‘Beeson’ soybean ( Glycine max L. Merr.) was grown 4 weeks, and the trifoliolate leaves evaluated for dry weight yield and for their Zn, Cd, and Mn concentrations. The higher organic matter Pocomoke soil was more effective than the Sassafras soil in reducing metal uptake and Zn phytotoxicity. Foliar Zn levels associated with yield reduction of soybean grown on Pocomoke differed with soil pH. Cadmium uptake was significantly lower on the Pocomoke soil. Foliar Mn increased to reported phytotoxic levels (&gt;500 mg/kg) with increased added Zn only on the Sassafras soil at pH 6.3. DTPA‐extractable Zn and Cd were linear functions of added Zn and Cd for both soils; 0.01 M CaCl 2 ‐extractable Zn and Cd were curvilinear (increasing slope) functions for the Sassafras and linear for the Pocomoke soil. Thus, soil type can strongly influence Zn, Cd, and Mn uptake, as well as Zn phytotoxicity to soybean. Soil organic matter appears to be more important than hydrous oxides of Fe and Mn in moderating the effects of excessive soil Zn and limiting Zn and Cd uptake. Induced metal toxicities (Mn) may depend on many factors, and should be considered an integral part of any characterization of specific metal phytotoxicities (e.g. Zn).

High freshwater flow delivers excess nutrients to Chesapeake Bay, leading to increased phytoplankton biomass, turbidity, and eutrophication. Low flow in 2002 was associated with a persistent drought that terminated abruptly in autumn 2002, followed by extremely high flow in 2003. This large difference in flow caused improved water quality in 2002 as nutrient loading subsided, and degraded water quality in 2003 with increased loading associated with high flow. We analyzed remotely sensed chlorophyll (chl a ) data using an online data analysis tool to quantify the effect of sequential low and high freshwater flow on phytoplankton biomass near the mouth of the Bay. Chl a in the study area was significantly higher in 2003 than in 2002, consistent with strong forcing by freshwater flow and nutrient loading in the nutrient‐limited region of the Bay.

Interannual variability of the spring phytoplankton bloom is strongly expressed in estuarine ecosystems such as Chesapeake Bay. Quantifying this variability is essential to resolve ecosystem responses to eutrophication from variability imposed by climate. We developed a 'synoptic climatology' from surface sea-level pressure (SLP) maps to categorize and quantify atmospheric circulation patterns and address climate forcing of phytoplankton dynamics in the Bay. The 10 patterns we identified had unique frequencies-of-occurrence and associated meteorological conditions (i.e. precipitation, temperature, wind speed and direction). Four measures of phytoplankton biomass, surface chlorophyll a (B), euphotic layer chlorophyll a (B eu ), water column chlorophyll a (B wc ), and total biomass (B tot ), were obtained from remotely sensed ocean color data spanning 16 yr (1989 to 2004) combined with concurrent shipboard data. Years with more frequent warm/wet weather patterns had spring blooms that reached peak biomass farther seaward in the estuary, were greater in magnitude, occurred later in the spring, and covered a larger area than years with a predominance of cool/dry weather patterns. Frequencies of winter weather patterns were used to forecast spring B, B eu , B wc , and B tot , explaining between 23 and 89% of the variance in the regional time-series. Residuals from these models did not show time-trends attributable to either accelerating eutrophication or management actions intended to decrease nutrient loadings. These findings extend our understanding of climatic influences on phytoplankton dynamics in the Bay by quantifying the effects of synoptic climate variability on spring bloom intensity, thereby supporting forecasts of seasonal phytoplankton biomass based on sub-continental scale weather patterns in this mid-Atlantic estuary.

Ocean color measurements from aircraft revealed an unusually strong fall bloom of phytoplankton in Chesapeake Bay after passage of Hurricane Isabel in September 2003. Flights conducted before (11 September) and after (24 September) Isabel showed a two‐fold increase of chlorophyll‐ a (Chl a ) covering ∼3000 km 2 of the mid‐ to lower Bay, with an abrupt return to long‐term average (LTA) Chl a by early October. Wind mixing induced rapid de‐stratification of the water column, injecting nitrogen (N) into the euphotic layer that supported a fall bloom of diatoms. Here we quantify a significant perturbation of the annual phytoplankton cycle in Chesapeake Bay, driven by Hurricane Isabel.

This chapter (i) documents the present status of polyculture systems being employed by the aquaculture industry, (ii) provides examples of balanced ecosystem approaches to aquaculture and fisheries, and (iii) examines the question of how to develop models for maximizing the production of seafood through fisheries and aquaculture working in harmony to minimize environmental impacts. The roles of microbes, marine plants, shellfish, finfish, and human communities in a balanced marine ecosystem are discussed.