Sensitivity analysis of a mathematical model of phytoplankton growth and nutrient distribution in the Pacific Ocean off the northwestern U.S. coast

In a recent publication (Jamart el al., Deep-Sea Research, 24,753–773, 1977) we describe a numerical two-dimensional(time and depth) model of phytoplankton growth and nutrientdistribution in the Pacific Ocean off the northwestern U.S.coast. The numerical model consists of coupled integro-partialdifferential equations expressing conservation of chlorophyll, nitrate, and ammonium. The relevant physical and biologicalprocesses are represented by conventional functions and parameters.The system is "closed" by specification of grazing pressureand light intensity. A long-term simulation ova spring and summermonths (for convenience, called the "standard run") representswell the main features of observed chemical data and biologicalvariables, including the formation and deepening of a subsurfacechlorophyll maximum. In this paper, a sensitivity analysis of the system is carriedout by comparing the "standard run" with the results of twentynumerical experiments, in each of which a single function orparameter in the model is modified. The formation of the subsurfacechlorophyll maximum is simulated, more or less realistically,in all experiments. Moreover, the results suggest that the chlorophylldistribution adjusts in time and depth so as to optimize thetransfer of carbon to secondary producers. The level of thecarbon output is determined mainly by the resources availableto the primary producers.     

太平洋中西部海域浮游植物营养盐的潜在限制

2009年8月至9月期间在太平洋西部N1站和中部N2站进行现场营养盐加富培养实验。结果显示:N1站,浮游植物生物量对N或者P添加都有较强的响应,其中N+P+Si组和N+P组浮游植物长势迅速,叶绿素a从初始的0.03μg/L分别达到2.12μg/L和1.83μg/L,同时P先于N和Si之前被耗尽;说明N1站为N、P共同限制,P是首要限制因子。而N2站,浮游植物生物量仅对N、P共同添加有明显响应,N先于P和Si被浮游植物消耗殆尽。利用培养过程中营养盐比值变化推断,N1站浮游植物以低于Redfield ratio(16N∶1P)吸收N和P;而N2站浮游植物以高于Redfield ratio(16N∶1P)吸收N和P。这可能解释了太平洋西部的寡营养盐海域为潜在P限制,而在太平洋中部海域则为潜在N限制。     

A mathematical model of the nutrient dynamics of phytoplankton in a nitrate-limited environment

Insofar as saturation kinetics are applicable to the growth of phytoplankton in laboratory experiments and to growth in nature, the computer modeling of intracellular nutrient partitioning in populations of cells can lead to better understanding of the dynamics of natural populations. A three-compartment mathematical model was developed to represent a phytoplankton population having the capability to store nitrogen in a nitrate-limited environment. Parameters were estimated by fitting the model to data from two chemostat experiments reported by Caperon (1968). The model was used to simulate growth dynamics observed in chemostat and batch experiments. The model demonstrated the changes which may occur in the nitrogenous constituents of a phytoplankton population with time and environmental conditions. The model also demonstrates three phenomena which have been observed in field and laboratory experiments but which are not represented by the customary Monod model: (1) uptake rates may significantly exceed not growth rates, (2) high growth rates may be encountered at very low environmental nitrate concentrations, and (3) the ratio of internal nitrogen to population size may change significantly during a study period. It is suggested that the amount of nitorgen in storage may be used as an indicator of the physiological state of a monospecific population. Parameters for the one-compartment Monod model were estimated by customary methods form data generated by the three-compartment model. It was shown that difficulties encountered in estimating the yield coefficient and the decay coefficient may be attributed to the intracellular storage phenomenon. It was also demonstrated that the one-compartment Monod model was inadequate to accurately represent population growth in chemostat experiments when intracellular storage is a significant factor.     

A mathematical model for insulin kinetics. III. Sensitivity analysis of the model

A non-linear mathematical model involving four variables and several constants incorporating beta-cell kinetics, a glucose-insulin feedback system and a gastrointestinal absorption term had been applied in earlier papers to various forms of diabetes mellitus. In this paper, we examine the response of the system to variations in the parameters and to initial conditions using sensitivity analysis. It is found that such a method leads to results that are consistent with clinical findings. Further, it is suggested that such an analysis could help in making some predictions regarding future directions in the therapy of diabetes mellitus.     

哥斯达黎加外海夏季表层浮游动物种类组成及分布

根据2009年7—8月在东热带太平洋哥斯达黎加外海(4°30’—10°24’N、91°20’—100°00’W)进行茎柔鱼探捕调查期间采集的表层浮游动物资料,对其种类组成、生物量及其分布进行了分析。结果表明,调查海域,鉴定出腔肠动物8目10科17属23种;甲壳动物8目30科43属74种;毛颚动物1目1科1属4种;尾索动物3目3科5属5种;环节动物为1目3科5属6种;软体动物1目1科3属3种;其他浮游动物有头足类的幼体、鱼卵和仔稚鱼以及浮游幼虫。调查海域总生物量和丰度的平均值分别为(124.78±176.83)mg/m3和(848±1219)个/m3,生物量较大的类群主要是甲壳动物的桡足类和毛颚动物的箭虫类其中桡足类的丰度(727个/m3)为最高,其次为箭虫类(373个/m3);出现频率较高的为桡足类、箭虫类、长尾类、头足类和鱼类仔稚鱼。     

Spatial Distribution and Conservation of Speckled Hind and Warsaw Grouper in the Atlantic Ocean off the Southeastern U.S.

There is broad interest in the development of efficient marine protected areas (MPAs) to reduce bycatch and end overfishing of speckled hind (Epinephelus drummondhayi) and warsaw grouper (Hyporthodus nigritus) in the Atlantic Ocean off the southeastern U.S. We assimilated decades of data from many fishery-dependent, fishery-independent, and anecdotal sources to describe the spatial distribution of these data limited stocks. A spatial classification model was developed to categorize depth-grids based on the distribution of speckled hind and warsaw grouper point observations and identified benthic habitats. Logistic regression analysis was used to develop a quantitative model to predict the spatial distribution of speckled hind and warsaw grouper as a function of depth, latitude, and habitat. Models, controlling for sampling gear effects, were selected based on AIC and 10-fold cross validation. The best-fitting model for warsaw grouper included latitude and depth to explain 10.8% of the variability in probability of detection, with a false prediction rate of 28–33%. The best-fitting model for speckled hind, per cross-validation, included latitude and depth to explain 36.8% of the variability in probability of detection, with a false prediction rate of 25–27%. The best-fitting speckled hind model, per AIC, also included habitat, but had false prediction rates up to 36%. Speckled hind and warsaw grouper habitats followed a shelf-edge hardbottom ridge from North Carolina to southeast Florida, with speckled hind more common to the north and warsaw grouper more common to the south. The proportion of habitat classifications and model-estimated stock contained within established and proposed MPAs was computed. Existing MPAs covered 10% of probable shelf-edge habitats for speckled hind and warsaw grouper, protecting 3–8% of speckled hind and 8% of warsaw grouper stocks. Proposed MPAs could add 24% more probable shelf-edge habitat, and protect an additional 14–29% of speckled hind and 20% of warsaw grouper stocks.     

Yessotoxin detected in mussel (Mytilus californicus) and phytoplankton samples from the U.S. west coast

Yessotoxin (YTX) was detected in an algal sample and two mussel samples (0.07–0.10 μg g⁻¹) collected from Scripps Pier in La Jolla, California during a bloom of Lingulodinium polyedrum. Mussel samples collected from Monterey Bay, California also contained measurable YTX (levels up to 0.06 μg g⁻¹) in samples obtained during a 6-month (weekly) sampling period. Gonyaulax spinifera and L. polyedrum were identified in background concentrations in Monterey Bay during the time of contamination. An algal sample from Washington coastal waters collected during non-bloom conditions also contained YTX, possibly originating from Protoceratium reticulatum.Three strains of L. polyedrum (CCMP1931, CCMP1936, 104A) isolated from southern California coastal waters and one strain of G. spinifera (CCMP409) isolated from Maine were tested for YTX production using two methods, competitive ELISA and liquid chromatography–mass spectrometry (LC–MS). The ELISA method detected YTX in the particulate phase in two of three L. polyedrum strains. The LC–MS method did not detect YTX in the particulate or dissolved phase of any of the strains.To our knowledge, this is the first study to test and confirm YTX in environmental samples from California and Washington coastal waters. It is highly likely that L. polyedrum was responsible for the YTX contamination in the southern California samples. Future research needs to conclusively determine the biological origin(s) of YTX contamination in central California and Washington coastal waters.     

Species-specific growth rate of phytoplankton in the West Pacific sector of the Southern Ocean. I.Prorocentrum scuttellum schröder

Phytoplankton samples were collected from the West Pacific Sector of the Southern Ocean to measure the growth rate from November 30 to December 1, 1995.Prorocentrum scuttellum was selected for growth rate measurement using the method of cell cycle analysis. During the 24 hr sampling cycle, cells ofP. scuttellum changed from 2,500 to 5,000 cells/L. The highest abundance was observed at 8:40 AM, December 1, and lowest at 11:40 PM, November 30. Cellular division seemed to occur sometime between 11:40 PM, November 30 and 2:40 AM, December 1. After cell division, DNA fluorescence shifted slowly towards the right, representing the S phase, and the majority of the cells were in S+G2 phases at 8:40 AM, December 1. Between the next six hours, a sharp drop in DNA fluorescence occurred, representing mitosis, and the majority of the cells returned to the G1 phase by 2:40 PM, December 1. We can not determine the duration time of the terminal event from this result However, the growth rate ofP. scuttellum was calculated as 0.43 d^-1 with the help of curve fitting methods. This unexpected result seems to have resulted due to background noise, unsynchronous cell division, unequal sampling, water column unstability, and migrating behavior ofP. scuttellum.     

Description of phytoplankton and nutrient in spring in the western North Atlantic Ocean

Abundance of diatoms in the northern Sargasso Sea in springhas been observed in a 4-year period between 1981 and 1985 andthen again in 1987. A theory is presented that if stratificationblocks get-through of deep nutrients to the surface, as in thesouthern Sargasso, then in-situ cycling via non-diatoms andammonia dominates. The theory is that if in-situ cycling doesnot dominate, as northward, then stratification does not blockget-through of deep nutrients to the surface, which, in combinationwith the marked growth capacity of diatoms, produce an abundanceof cells. This abundance consumes nitrate, phosphate and silicateat the surface and ultimately this nutrient-depleted water arrivesin the southern Sargasso via the gyre circulation. Thus thenutrient-depleted water of the western Atlantic gyre is consideredto be primarily achieved only by diatoms, in spring and in thenorthern Sargasso. A transect during April 13–16, 1985,north from the Virgin Islands along 63°–64°W showsa great change in the diatom species plus Emiliania huxleyifrom negligible concentrations in the southern half of the sectionto large concentrations in the northern half. This unevennessof distribution can be rephrased by indicating that these speciesare narrow-niched with regard to nutrient availability. Theother species, coccolithophores and dinoflagellates, are evenlydistributed at low concentrations south-north (though some diminishslightly) and so they are broad-niched with respect to nutrient.High species diversity depends on broadness of nutrient nicheand equilibrium conditions of hydrographically stable water(i), implying that when non-equilibrium conditions occur (ii),when niche breadth is less (iii) or both (iv), then diversityis less marked, (i) is confirmed by broad-niched species southward,(ii) is confirmed by broad-niched species northward, (iii) isconfirmed by narrow-niched species southward and (iv) by narrow-nichedspecies northward.     

Geographic variation in the maturity and growth schedules of English sole along the U.S. west coast

Logistic regression analyses showed that the maturity v. length relationship for female English sole Pleuronectes vetulus varied significantly among sampling locations from California to British Columbia in June–September. Stepwise analyses found that latitude, bottom gradient, bottom temperature and sediment type were all significant factors. Regression analyses of age at length from subsamples indicated that latitude, maturity and bottom sediment had significant effects on growth. Data from the aged subsamples showed significant differences among age classes in the length v. maturity relationship with older fish attaining maturity at smaller sizes than younger fish. On a coast wide basis the length and age at 50% maturity were c. 230 mm and 4·7 years respectively. Growth rate and length at 50% maturity have decreased substantially relative to observations from the 1950s, but age at 50% maturity has increased.     

Growth and mortality rates of phytoplankton in the northwestern North Pacific estimated by the dilution method and HPLC pigment analysis

Pigment-based growth rates of phytoplankton and mortality rates due to microzooplankton grazing were estimated using a dilution method combined with high-performance liquid chromatography (HPLC) pigment analysis in the northwestern North Pacific in autumn 1998. The dilution experiments were conducted at different hydrographic stations in both colder and warmer water masses. No significant difference was found between the growth rate of the phytoplankton community (0.38–0.70 day⁻¹; estimated by chlorophyll a) at the colder and warmer water stations, while the mortality rate (0.15–0.88 day⁻¹; estimated by chlorophyll a) tended to be higher at warmer water stations. The combination of estimates of daily chlorophyll a production and particulate organic carbon (POC) production enabled us to assess the carbon to chlorophyll a ratio (C/chl a) of “new” organic matter produced by living phytoplankton. The method provided an implicit value of the C/chl a of in situ living phytoplankton. The rate estimates from taxon-specific pigments suggested a possibility that chlorophyll b-containing green algae were grazed preferentially by microzooplankton during their active growth, and the standing stock of green algae was more strictly controlled by micrograzer than other algal groups such as diatoms. This result is one possible explanation for the fact that blooms of green algae have not been reported in the open ocean, in contrast with diatoms.     

Larval fish assemblages in waters off the central Pacific coast of Mexico

Spatial and seasonal variation of the ichthyoplankton assemblageswas analysed using monthly samples collected during a 1 yearcycle off the central Pacific coast of Mexico. Zooplankton sampleswere collected at 12 stations during 11 months, from December1995 to December 1996. The analysis of coastal oceanographicconditions revealed two main seasonal patterns, one relatedto the California Current influence and the other a tropicalone. A temporal recomposition of the ichthyoplankton assemblageswas found to be related to each oceanographic pattern. Duringthe California Current period (January–May) the larvalfish assemblage was respresented mainly by Auxis sp., Bentosemapanamense, Cetengraulis mysticetus, Opistonema sp., Symphuruselongatus, Gobionellus sp., Dormitator latifrons and Bregmacerosbathymaster. The tropical season assemblage (July, October andNovember) was represented by Harengula thrissina, Euthynnuslineatus, Vinciguerria lucetia, Syacium ovale, and representativesof the Eleotridae and Pomacentridae. An inshore–offshoregradient was observed during the tropical oceanographic periods,with a thermic stratification of the water column over the shelf.Conversely, during the California Current period, with coastaladvective processes, the assemblages of fish larvae were morehomogeneous. Although a mixed, richer faunistic compositionwas expected in this transitional area, the overall biogeographicaffinity of the surveyed community remained stable even in contrastingconditions.     

Oxidative stress indicators and trace elements in the blue shark (Prionace glauca) off the east coast of the Mexican Pacific Ocean

Trace element concentrations and oxidative stress indicators (including production of reactive oxygen species (ROS), antioxidant enzyme activities and oxidative damage) were measured in muscle of blue sharks collected along the west coast of Baja California Sur to determine potential differences by sex and maturity cohorts. Mercury (Hg) concentration in muscle samples from larger sharks (>200 cm LT) exceeded the permissible limit (>1 ppm wet weight) for human consumption set by numerous international agencies. Significant differences were found in Hg concentrations (mature>immature; males>females), and in protein carbonyl concentrations (male>female); however, except for carbonyl protein levels, no significant differences by sex or maturity stage were found in the oxidative stress indicators. Differences between sexes and maturity stages in trace element concentration and carbonyl protein levels in blue shark muscle may be related to variations in diet within different cohorts.     

Antitropical distribution and evolution in the Indo-West Pacific Ocean

Antitropical distributions of continental shelf, Indo-West Pacific species are probably not due to transgression of the tropics during the glacial periods, isothermic submergence, island integration, rising Neogene temperatures, or the Mesozoic dispersal of fragments from a Pacific continental mass. Characteristics of common antitropical patterns, plus information from systematic works on a variety on a variety of animal and plant groups, indicate that the long discarded "relict theory" of Theel (1885) appears to best fit the evidence, for it provides a mechanism whereby antitropical distribution may be brought about. The relict theory is compatible with the concept that the East Indies part of the Indo-West Pacific has been functioning as a center of evolutionary origin. It suggests that antitropical and associated disjunct patterns are produced as an older species, that has spread out to occupy a broad range, loses ground and gradually becomes supplanted by a younger species that had subsequently evolved in the East Indies. As this process goes on, the older species becomes restricted to a few isolated localities on the fringe of its original range. These isolates are often found to the north and south of the equatorial region but may include relict populations at the western edge of the Indian Ocean.     

The food supply of the Pacific salmon of the genus Oncorhynchus in the northwestern Pacific Ocean. 2. Comparative characterization and general state

The interannual variations and general state of the food supply of Pacific salmon (Oncorhynchus spp.) in the 2000s in the northwestern Pacific Ocean (including the Bering Sea and the Sea of Okhotsk) were analyzed based on indirect characteristics that indicate the variability of their forage base, feeding habits, growth, and biomass. A new index for the quantitative evaluation of food supply was suggested. The food supply of the Pacific salmon during the 2000s was found to be sufficient to maintain the normal functioning of populations. With high abundance of Pacific salmon, the food supply tended to decrease. However, this caused no negative consequences for the survival of major salmon stocks during the marine period of life and, as a rule, no marked decrease in the food consumption and growth rates of fish. A relative increase in food competition was compensated by adaptive changes in the diet and diel feeding rhythm of salmon. With the shortage of preferred food organisms (amphipods, euphausiids, and pteropods), Pacific salmon changed to consuming minor prey (copepods and chaetognaths), and numerous mesopelagic species of macroplankton and micronekton in the evening hours.     

Comparison of phytoplankton concentrations and cell volume measurements from the continental shelf off Cape Cod,Massachusetts, U.S.A.

Phytoplankton composition and concentrations varied at stations across the shelf with maximum phytoplankton volumes not necessarily related to maximum concentration values. The shelf phytoplankton off Cape Cod, Massachusetts was composed of two major size classes: the ultraplankton (cells less than 10 microns in size), and net phytoplankton. Cell concentrations decreased along transects seaward, to increase near the shelf margin. Higher cell volume values coincided with increased cell counts east of Cape Cod, but were lower southward, increasing in the mid-shelf region, to decrease along the shelf margin. The shelf ultraplankton component typically represented over 90% of the standing crop, but less than 1% of its phytovolume. Associations are made between cell volumes and concentration combinations and different phytoplankton assemblages.     

Light and nutrient availability affect the size-scaling of growth in phytoplankton

Communities of marine phytoplankton consist of cells of many different sizes. The size-structure of these communities often varies predictably with environmental conditions in aquatic systems. It has been hypothesized that physiological differences in nutrient and light requirements and acquisition efficiencies contribute to commonly observed correlations between phytoplankton community size structure and resource availability. Using physiological models we assess how light and nutrient availability can alter the relative growth rates of phytoplankton species of different cell sizes. Our models predict a change in the size dependence of growth rate depending on the severity of limitation by light and nutrient availability. Under conditions of growth-saturated resource supply, phytoplankton growth rate (mol C ) scales with cell volume with a size-scaling exponent of ; light limitation reduces the size-scaling exponent to approximately , and nutrient limitation decreases the exponent to as a consequence of the size-scaling of resource acquisition. Exponents intermediate between and occur under intermediate availability of light and nutrients and depend on the size-scaling of pigment photoacclimation and the size range examined.     

Patterns in species richness,species density,and evenness in groundfish assemblages on the continental slope of the U.S. Pacific coast

For many taxa, diversity, often measured as species richness, decreases with latitude. In this report patterns of diversity (species richness, species diversity, and evenness) in groundfish assemblages were investigated in relation to depth (200–1200 m) and latitude (33–47°N) on the continental slope of the U.S. Pacific coast. The data originated from the 1999–2002 upper continental slope groundfish surveys conducted by the National Marine Fisheries Service. When the data were pooled across depths, species density and evenness were found to decline with latitude. All three diversity measures declined with depth, with the lowest overall diversity in the 600- to 900-m depth range where longspine thornyhead Sebastolobus altivelis constituted close to 70% of the catch. When latitudinal gradients were examined within four depth zones (200–300 m, 400–500 m, 600–900 m, and 1000–1200 m) more complex patterns emerged. At depth species richness and evenness were inversely correlated with latitude as longspine thornyhead dominated catches to the north. However, in shallower areas of the slope, species richness and evenness were positively correlated with latitude. Latitudinal patterns of diversity in the deeper zones and when pooled across depths were positively correlated with temperature and broadly consistent with the Ambient Energy hypothesis discussed by Willig et al. [Annu Rev Ecol System 34:273–309 (2003)].