Abstract: In the past decade, there has been growing interest in understanding the physiological ecology and life cycle of toxic forms of Pfiesteria piscicida. However, transformations among non-inducible (NON-IND; formerly described as nontoxic) stages have received less attention despite the fact that NON-IND stages are found in nature and may be ecologically important as prey and predators. NON-IND stages are also mixotrophic and have the ability to retain and utilize prey chloroplasts in a process termed 'kleptoplastidic mixotrophy'. Quantifying growth, grazing and encystment rates from P. piscicida laboratory experiments is confounded by the interrelationship between mixotrophy and life stage transformations. By fitting a numerical model to a laboratory experiment on NON-IND P. piscicida, we were able to isolate the potential mechanisms that cause encystment and speculate on the interrelationship between adverse conditions (i.e. low light and limiting prey) and life stage transformations. The structure of the laboratory experiment allowed for the estimation of several growth and encystment parameters including grazing rates, gross growth and assimilation efficiencies, as well as the retention time of chloroplasts. Model results suggest a link between encystment and mixotrophic ability. Furthermore, the model results suggest that encystment rates and gross growth and assimilation efficiencies calculated from the model are lower than expected.

Abstract: Mesozooplankton growth rates were estimated for the Hawaiian (HOT) and Bermuda (BATS) ocean time-series stations using the empirical model of Hirst and Lampitt (Marine Biology 132 (1998) 247), which predicts copepod growth rate from temperature and body size. Using this approach we derived seasonal and annual estimates of mesozooplankton production as well as rates of mesozooplankton ingestion and egestion using assumed growth and assimilation efficiencies for the period 1994-1997. Annual mesozooplankton production estimates at HOT (average 0.79 Mol C m(-2) yr(-1)) were higher than production estimates at BATS (average 0.3 3 mol Cm-2 yr(-1)) due to both higher mesozooplankton biomass and higher estimated mesozooplankton individual growth rates. Annual primary production at the two sites was similar (average 14.92 mol Cm-2 yr(-1) at HOT and 13.43 mol Cm-2 yr(-1) at BATS). Thus, mesozooplankton production was a greater fraction of primary production at HOT (0.05) as compared to BATS (0.02). Mesozooplankton potentially contributed more to the gravitational flux of carbon at HOT, where the ratio of the average annual estimate of mesozooplankton fecal pellet carbon production/annual estimate of carbon flux at the base of the euphotic zone was 1.03 compared to the same ratio of 0.39 at BATS. Mortality estimates were similar to estimates of mesozooplankton production when compared over the entire study period. The higher mesozooplankton biomass and derived rate parameters at HOT compared to BATS may be due to the more episodic nature of nutrient inputs at BATS, which could result in mismatches between increases in phytoplankton production and the grazing/production response by mesozooplankton. In addition, there is evidence to suggest that there are periodic blooms of gelatinous macrozooplankton (salps) at BATS that may not be captured sufficiently by the monthly sampling program. Thus the gelatinous zooplankton would add to the overall grazing impact on the phytoplankton at BATS as well as the contribution of zooplankton to the gravitational flux of biogenic material via fecal pellet production. (C) 2001 Elsevier Science Ltd. All rights reserved.

Abstract: Pigment ingestion rates by three size classes of mesozooplankton (200-500 mu m, 500-1000 mu m and 1000-2000 mu m) within the euphotic zone were measured during the Survey 1 (February/March) and Survey 2 (August/September) cruises of the 1992 United States Joint Global Ocean Flux Study (U.S. JGOFS) in the central equatorial Pacific (EqPac). Survey 1 was characterized by El Nino conditions while Survey 2 was characterized by typical climatological conditions, The small animals (200-500 mu m) contributed more than 50% (range: 34-80%) to the total mesozooplankton grazing reported here. Mesozooplankton grazing was higher within the equatorial region (5 degrees S-5 degrees N) than at higher latitudes (5 degrees S-12 degrees S, 5 degrees N-12 degrees N). The carbon-specific ingestion rates of both the large and small animals tended to be higher during Survey 1 than during Survey 2. In contrast to the carbon-specific ingestion rates, the mesozooplankton biomass during Survey 1 was lower than that during Survey 2. Thus, the higher ingestion rates during Survey 1 were offset by lower biomass and the mesozooplankton grazing was quite similar during Surveys 1 and 2. Mesozooplankton removal of chi a was higher within the high-phytoplankton-biomass equatorial region than at higher latitudes during Survey 1, but regional differences were not significant during Survey 2. Mesozooplankton community grazing was equivalent to an average daily removal of 3.0% (range: 0.5-7.7%) and 2.2% (range: 0.8-3.5%) of the total chi a standing stock within the euphotic zone during Surveys 1 and 2, respectively. However, mesozooplankton grazing was equivalent to a daily removal of 47% (range: 15-91%) and 36% (range: 23-66%) of the > 5 mu m chi a standing stock within the euphotic zone during Surveys 1 and 2, respectively. Assuming a carbon-to-chi a ratio of 58, we estimate that mesozooplankton grazing removed an average of 6% (range: 2-12%) of C-14 primary production during Survey 1, and 5% (range: 2-10%) during Survey 2. Removal rates were not significantly different between the equatorial region and the higher latitudes. Rates of respiration and ammonium excretion were estimated from empirical models based on animal weight and water temperature. Phytoplankton ingestion could not satisfy the estimated daily maintenance-carbon demands of mesozooplankton. The shortages were more pronounced in the large size fraction than in the small size fraction. The estimated ammonium excretion by the mesozooplankton could support 4-15% and 3-17% of C-14 primary production during Surveys 1 and 2, respectively.

Abstract: In China, agricultural residues (particularly from rice) are widely used for energy and other applications, albeit on a localized scale and often at poor rates of efficiency. if some portion of this biomass were to be reallocated and transported to central biomass energy facilities, an initial component of the design process would be to gain an understanding of the spatial distribution of biomass production. In this paper, we present a method that utilizes China-wide data sets of net primary production (NPP) from the moderate-resolution imaging spectrometer (MODIS) and detailed land cover maps produced from Landsat-enhanced thematic mapper plus (ETM+) data to calculate the spatial distribution of rice straw for the period 2000-2004. Through a comparison with census statistics, we show that remote measures of rice straw can reasonably predict census results at the provincial scale. Remote sensing results have the added benefits of being a quick and inexpensive solution for providing spatially detailed information. Therefore, these data can be used for applications such as the spatial optimization of energy production infrastructure. In an error analysis including climate and land use variables, we found that data on sown rice area is the largest source of error. Therefore, the most important improvement to this method would be more accurate and more frequently updated maps of agricultural land use. (c) 2007 Elsevier Ltd. All rights reserved.

Abstract: The northern Gulf of Mexico (NGOMEX) was surveyed to examine the broad-scale spatial patterns and inter-relationships between hypoxia (< 2 mg L-1 dissolved oxygen) and zooplankton biovolume. We used an undulating towed body equipped with sensors for conductivity, temperature, depth, oxygen, fluorescence, and an optical plankton counter to sample water column structure, oxygen, and zooplankton at high spatial resolution (1 m-vertical; 0.25-1 km-horizontal). We contrast the distribution of zooplankton during summer surveys with different freshwater input, stratification, and horizontal and vertical extent of bottom-water hypoxia. Bottom-water hypoxia did not appear to influence the total amount of zooplankton biomass present in the water column or the areal integration of zooplankton standing stock in the NGOMEX region surveyed. However, where there were hypoxic bottom waters, zooplankton shifted their vertical distribution to the upper water column during the day where they normally would reside in deeper and darker waters. When bottom waters were normoxic (> 2 mg L-1 dissolved oxygen), the daytime median depth of the water column zooplankton was on average 7 m deeper than the median depth of zooplankton in water columns with hypoxic bottom waters. A reduction in larger zooplankton when there were hypoxic bottom waters suggests that if zooplankton cannot migrate to deeper, darker water under hypoxic conditions, they may be more susceptible to size-selective predation by visual predators. Thus, habitat compression in the northern Gulf of Mexico due to hypoxic bottom water may have implications for trophic transfer by increasing the contact between predators and prey.