Uptake of nitrogenous nutrients by phytoplankton in a barrier Island estuary: Great South Bay,New York

The uptake of urea, nitrate and ammonium by phytoplankton was measured using ¹⁵N isotopes over a one-year period in Great South Bay, a shallow coastal lagoon. The bay is a unique environment for the study of nutrient uptake since ambient concentrations of $\text{NO}{}_3{}^{\mathrm{?}}\text{NH}{}_4{}^{\mathrm{+}}$ and urea remain relatively high through the year, and phytoplankton are probably never nutrient limited. Urea nitrogen averaged 52% of the total assimilated, while ammonium represented 33% and nitrate 13%. High rates of ammonium uptake occurred only at low urea concentrations (ca< 1-μg-atom urea l^?1). Over the sampling period urea was present in relatively high concentrations, averaging 5·35 μg-atom N l^?1, while means for ammonium and nitrate averaged 1·94 and 0·65 μg-atom N l^?1, respectively. Total N uptake measured with ¹⁵N averaged about 3·3 times the calculated (from elemental ratios and ¹⁴C productivity measurements) N needs of the phytoplankton population. Highest nitrogen uptake occurred in the summer and coincided with the primary production maximum.     

Particulate organic matter in the coastal and estuarine waters of Goa and its relationship with phytoplankton production

In the coastal and estuarine waters of Goa, particulate organic carbon (POC) varied from 0.52 to 2.51 mg l^?1 and from 0.28 to 5.24 mg l^?1 and particulate phosphorus (PP) varied from 0.71 to 5.18 μg l^?1 and from 0.78 to 20.34 μg l^?1, respectively. The mean values of chlorophyll and primary productivity were 1.94 mg m^?3 and 938.1 mg C m^?2 day^?1 in the coastal waters and 4.3 mg m^?3 and 636.5 mg C m^?1 day^?1 in the estuarine waters, respectively.$\text{POC}\text{chl}$ ratios were low in June and October even when POC values were quite high. The POC in surface waters was linearly correlated with the chlorophyll content. Also PP increased when chlorophyll and primary productivity remained high. The results suggest that the phytoplankton was sharply increasing and contributed to POC and PP content. The percentage of detritus calculated from the intercept values of chlorophyll on POC varied from 46 to 76% depending on season. Results indicate that the major portion of POC and PP during postmonsoon (October–January) is derived from phytoplankton production while the allochthonous matter predominate during monsoon (June–September).     

Microbial nitrogen transformations in sediments and inorganic nitrogen fluxes across the sediment/water interface on the South Island West Coast,New Zealand

In January 1982, sediment microbial N transformations and inorganic N fluxes across the sediment/water interface were studied at nine sites off the South Island West Coast, New Zealand. The sediments showed a great variety in physical, chemical and biological properties. The sediment organic matter had a molar $\text{C}\text{N}$ ratio of 5.9–10.9, and the total $\text{N}\text{P}$ ratio was 1.2–4.0. The denitrification capacity in the top 7.5 cm of sediment was 0.1–77.2 mmol N m^?2 day^?1 and generally declined with increasing sediment depth. The in situ denitrification rate was 0.02–1.84 mmol N m^?2 day^?1 and highest activities were generally found in surface sediments and at 6–7.5 cm depth. Denitrification accounted for 82–100% of total nitrate reduction. Net N mineralization was indirectly estimated at 0.6–2.4 mmol N m^?2 day^?1, and the experimental determination of this N transformation gave 0.6–3.2 mmol N m^?2 day^?1. Denitrification accounted for 3–75% of net N mineralization. The diffusive flux of ammonium and nitrate across the sediment/water interface was 0.1–0.7 and 0.1–0.6 mmol N m^?2 day^?1, respectively.     

Particulate protein measurement in oceanographic samples by dye binding

A modified version of the Coomassie Brilliant Blue dye binding protein assay has been developed for oceanographic samples and intercalibrated with the widely used Lowry assay. Particulate protein measurements were made at seven stations in the Gulf of Maine using the method. Measurements were made on cell-free homogenates. Protein concentration ranged from 2 to 212 μg l^?1 (0.02–0.68 μg at N l^?1) and averaged 58 μg l^?1. ETS activity, chlorophyll and particulate nitrogen were significantly correlated with protein concentrations.     

Enteromorpha and the cycling of nitrogen in a small estuary

The nitrogen relations of Enteromorpha spp. growing on intertidal mud flats have been examined over a twelve-month period. Nitrogen assimilation rates using ¹⁵N have been used to calculate the production of the alga and were between 0·046 and 0·217 mg $\text{NH}{}_4{}^{\mathrm{+}}\text{N}$ (g dry wt alga)^?1 h^?1 A considerable quantity of the alga was buried beneath the sediment over the growth season and was calculated to be equivalent to an input of up to 9·52 g N m^?2 per month and 32 g N m^?2 over one complete growth season. Based on carbon, this latter value represented an input of approximately 320 g C m^?2 annually. Low rates of nitrogenase activity (acetylene reduction) were found to be associated with the Enteromorpha. The organisms responsible for the nitrogenase activity were probably heterotrophic bacteria but they did not contribute significant quantities of nitrogen to the alga.     

Estimation of benthic respiration parameters from field data

Seasonal benthic respiration rate observations from Chesapeake Bay and the Patuxent estuary have been used to determine the benthic decay coefficient. Non-linear parameter estimation procedures were employed to delineate the optimal values and associated confidence intervals for the microbial decay and macrofaunal respiration parameters. The results demonstrate that microbial decay of organic detritus on the bottom is a long-term process with a yearly averaged decay coefficient of around k = 0·0056 day^?1 ($\text{τ =}\text{1}\text{k}\text{= 180}\text{day}$).     

Trace metals in the Göta river estuary

The concentrations of the trace metals Cd, Cu, Fe, Ni, Pb and Zn in the Göta River estuary have been investigated. The following metal fractions have been determined: acid-leachable, dissolved, labile and particulate.The estuary represents a salt wedge type estuary and is situated in a densely populated region of Sweden. The metal concentrations found for the dissolved fraction is in the range of what can be considered as background levels for freshwater. It is difficult to evaluate any estuarine processes other than conservative mixing for Cd, Cu, Ni and Zn. The dissolved levels in the freshwater end member are Cd, 9–25 ngl^?1; Cu, 1·1–1·4 μgl^?1; Fe, 20–75 μg l^?1: Ni, 0·7–0·9 μg l^?1: Pb 0·09–0·2 μg l^?1; and Zn, 6–7 μg l^?1:The results from the acid-leachable fraction show that at high suspended load the particles sediment in the river mouth. The trace metal levels in this fraction are subject to large variations.     

210Pb in a tropical coastal lagoon sediment core

Excess ²¹⁰Pb in a core from a Mexican Coastal Lagoon, which has no connection with the sea shows a small but measurable decay over the length of the core, when different approaches were compared (excess and corrected ²¹⁰Pb activity with depth, total and inorganic cumulative weights) significant differences in the values for the sedimentation rate are obtained. The best coefficient correlation was calculated when corrected ²¹⁰Pb activity for the uneven distribution of organic matter and cumulative inorganic weight is considered ($\text{ω}\text{= 0·93 cm yr}{}^{\mathrm{?1}}$, R = ?0·86; ω = 0·51 cm yr^?1 for the top 13 cm, R = ?0·90 and 1·52 cm yr^?1 for the interval 14–46 with R = ?0·96).Time frames in the sedimentary column were in agreement between the ²¹⁰Pb calculated time and the appearance of shells fragments probably associated with the disturbances caused by the 1961 hurricane Tara.The surface accumulation rate is equivalent to a mean deposition of 262·5 g m^?2 yr^?1 or organic matter which is minor but comparable to some salt marshes of United States.     

Nitrogen losses from a Louisiana Gulf Coast salt marsh

Losses of ¹⁵N labelled nitrogen in a Spartina alterniflora salt marsh was measured over three growing seasons. Labelled $\text{NH}{}_4{}^{\mathrm{+}}\text{N}$ equivalent to 100 μg ¹⁵N g^?1 of dry soil was added in four instalments over an eight week period. Recovery of the added nitrogen ranged from 93% 5 months after addition of the $\text{NH}{}_4{}^{\mathrm{+}}\text{N}$ to 52% at the end of the third growing season which represented a nitrogen loss equivalent to 3·4 gNm^?2. The availability of the labelled $\text{NH}{}_4{}^{\mathrm{+}}\text{N}$ incorporated into the organic fraction was estimated by calculation of the rate of mineralization. The time required for mineralization of 1% of the tagged organic N increases progressively with succeeding cuttings of the S. alterniflora and ranged from 152 to 299 days. Only 2% of the nitrogen applied as ¹⁵N labelled plant material to the marsh surface in the fall could be accounted for in S. alterniflora the following season.     

Nitrification and the enumeration of marine nitrifying bacteria in a closed prawn-culture system

Nitrification in a closed prawn-culture system was well established and followed the classical oxidation sequence of ammonia via nitrite to nitrate. Ammonia levels were in the range 4,8–68,7 μg-at N·?^?1 nitrite 0,15–891 μg-at N·?^?1 and nitrate approached a maximum of 9 898 μg-at N·?^?1 after 22 weeks. Marine nitrifying bacteria were enumerated by the most probable number (MPN) technique. The maximum MPN estimate of either group of nitrifying bacteria in the filter was 1,73 × 10⁷·cm^?3 while the maximum MPN estimate of their counterparts in the culture water was approximately 500 times lower. To establish mean incubation times for the accurate enumeration of nitrifying bacteria, incubations were carried out over a period of 130 days. Maximum estimates of MPN of ammonia-oxidizing bacteria were obtained after an incubation period of 20 days with a mean of 15 days. Nitrite-oxidizing bacteria required a maximum of 65 days with a mean incubation period of 30,3 days.     

Upwelling in the Southern Benguela Current

This survey of the southernmost significant upwelling site in the Benguela Current showed that the oceanography is dominated by the seasonal wind cycle of predominant S-E winds in summer and N-W winds in winter. In the upwelling season, extending from September to March, a semi-permanent plume is isolated by a pronounced oceanic front whose position varies in the short-term and is related to wind direction. Surface waters change immediately and deeper waters more slowly to fluctuations in wind. The rate of upwelling was statistically related to wind data. A maximum rate of 32 m day^?1 was found.In spring low temperature and salinity water flows northward on the shelf while between late summer and later winter oxygen-depleted water, rich in nutrients, flowed south at an estimated rate of 7–21 × 10⁴ m³ s^?1 in a counter current to the Good Hope Jet.Local depletion of oxygen occurs due to phytoplankton decomposition caused, in autumn, by falling light levels and, in summer in calm periods, by nitrate depletion (<1 μg-at N 1^?1). Primary productions is estimated at 3.7 kg C m^?2 yr^?1 with a maximum growth rate (PI_max) = 17.4–19.0 mg C mg chlorophyll a^?1 hr^?1 and half-saturation constant (K_S) = 0.4–1.1 μg-at N 1^?1. Nutrients were utilized and oxygen produced: ΔP:ΔN:ΔSi:ΔO=1:19.1 to 23.3:17.5 to 23.3:?227 to ?293. High N:Si ratios (maximum 4.28) were found in oxygen-depleted water produced locally while that coming from the north had low ratis, due to resolution of silica from the sediments and nitrate reduction. The mean zooplankton standing stock, 2.3 g dry weight m^?2, was 12% of the phytoplankton crop. In summer stocks were maximal 40–100 km and minimal 20–50 km from the coast while in winter they were maximal inshore. Little vertical migration occurred and the waters above the thermocline contained the majority of the population.     

Bacterial populations,heterotrophic potentials,and water quality in three New Zealand Rivers

Abstract

Thirty sites were sampled in three New Zealand rivers (Waikato, Maitai, and Wakapuaka) during late summer 1977. Samples were collected from just below the surface at mid river or in the tailraces below hydro‐electric dams.

Parameters measured included bacterial numbers (direct counts), heterotrophic potential (V_max ), adenosine triphosphate (ATP), chlorophyll a (Chi a), and concentrations of nitrogen and phosphorus compounds.

Bacterial populations per millilitre fluctuated threefold (6.4–19.4 × 10⁵) along the Waikato River and were lower and more consistent in the two South Island rivers (1.46–2.55 × 10⁵). In contrast, V_max varied 5000‐fold in the Waikato River, from a characteristically oligotrophic value of 0.0035 μg. l^?1·h^?1 (Lake Taupo outlet) to a eutrophic value of 18.4 μg. l^?1·h^?1 at the Mihi bridge. V_max for the two South Island rivers ranged from 0.0091 to 0.189 μg. l^?1 · h^?1.

ATP, Chi a, Kjeldahl nitrogen, nitrate nitrogen, and total phosphorus concentrations for the 20 sites on the Waikato River varied in a similar way to the V_max and bacterial data. There were large peaks at the Mihi bridge, lower values for the dam tailraces and significant increases for the sites below Hamilton. Concentrations for these parameters were lower and more consistent along the lengths of the two South Island rivers.

Most parameters were significantly correlated with each other for the Waikato River samples. The strongest correlations were between V_max and bacterial numbers and between V_max and nitrate nitrogen. In the Maitai and Wakapuaka River series these correlations were also significant, but the only other significant correlations recorded there were between ATP and nitrate nitrogen, and between ATP and bacterial numbers.     

Accumulation of Zn,Cu and Cd by crabs and barnacles

The crab Carcinus maenas (L.) and the barnacle Elminius modestus Darwin were exposed to a range of dissolved concentrations of Zn, Cu and Cd for 21 days in artificial seawater. Accumulation of Zn and Cu by crabs has been interpreted in terms of the presence of a regulation mechanism to maintain constant body concentrations (83·2 ± 19·4 μg Zn g^?1 dry wt.; 39·8 ± 9·8 μg Cu g^?1 dry wt.) under varying external dissolved metal levels, until a threshold dissolved metal concentration (c. 400 μg Zn l^?1; c. 170 μg Cu l^?1) beyond which net accumulation of metal begins. Cadium appears to be accumulated by C. maenas at all exposures with no evidence for regulation of body cadmium concentrations. Exposure of E. modestus to Zn, Cu or Cd caused net accumulation of the respective metal in the bodies of the barnacles, with no evidence for regulation of body metal concentrations.     

Abundance,community composition,size distribution,and production rates of tintinnids in Narragansett Bay,Rhode Island

The abundance of tintinnid ciliates in lower Narragansett Bay was measured at weekly intervals over the period 1980–1982. Twenty-nine species representing nine genera ranged in abundance from 10¹ to 10⁵ tintinnids l⁻¹. Tintinnopsis was the most numerous genus in terms of numbers of species and individuals. Total abundance increased with water temperature above 6°C, and with nanoplankton chlorophyll a (<10 μm and <5 μm chl a) averaged over the water column. Exceptions occurred during blooms of phytoplankton previously demonstrated to be poor food for tintinnids (Olisthodiscus, Thalassiosira). Tintinnids aggregated near the bottom during periods of low nanoplankton chl a. Abundances and distributions were not correlated with particulate organic carbon. Seasonal changes in length and oral diameter of loricas of individual species were inversely related to temperature. Oral diameter was a more constant feature of lorica morphology than length. Seasonal patterns in the mean oral diameter of the lorica of all species reflected decreases in the oral diameter of individual species with increasing temperature, and changes from small to large species coincident with similar shifts in the size of phytoplankton. The production rate of tintinnids was 3·3 mgCl⁻¹ year⁻¹, equivalent to the ingestion of 26% of total annual net primary production and 52% of the estimated production of <10 μm phytoplankton.     

δ13C analyses of oceanic particulate organic matter

Seventy-nine δ¹³C analyses of oceanic particulate matter (> 0·μ) from semi-tropical (Gulf of Mexico, Caribbean and Atlantic) and polar (South Indian Ocean) waters showed that the carbon isotope composition of the particulate matter from the cold polar surface waters was lighter ($\text{?24·7}\text{to}\text{?26·0‰}$) than that from the surface in the semi-tropical regions ($\text{?19·8}\text{to}\text{?22·3 ‰}$), reflecting the temperature effect on the photosynthetic fixation of carbon. δ¹³C for deep samples (> 330 m) were generally more negative than the surface samples, except in some well-mixed polar areas.A difference both in organic carbon isotopic composition and percentage organic carbon in the POM and the tops of sediment cores was also apparent; a loss of approximately 95 % of incoming carbon and an increase in ¹³C of several per mille being observed during deposition of particulate matter. This indicates that after settling on the bottom there is extensive diagenesis of the POM by organisms, indicating the non-refractory nature of the organic matter.     

Seasonal fluctuations and compositions of two populations of small demersal fishes on the west coast of Scotland

The soft sediment fish communities below 20 m depth were studied at two sites on the west coast of Scotland (Irvine Bay, Firth of Clyde and the Lynn of Lorne) using small meshed beam trawls. In both cases the emphasis was on the small demersal fish (<15 cm) within these communities. The Irvine Bay community was studied between May 1978 and December 1979 and the Lynn of Lorne community between February 1975 and October 1976.Twenty-seven fish species were recorded in Irvine Bay and 32 in the Lynn of Lorne. In both communities four species constituted more than 78% of the total annual abundance, two gobies (Lesueurigobius friesii and Pomatoschistus norvegicus) were high in the dominance ranking for both sites. The species abundance lists were similar for both sites (0·62 level of similarity) but the species lists for each site were different (0·36 level of similarity). The overall mean density of small demersal fish was similar for both sites (Irvine Bay = 0·045 individuals m^?2 and the Lynn of Lorne = 0·047 individuals m^?2). There were two periods of high abundance for both communities (late autumn to winter and late spring). There was, however, a low repeatability between successive years. The species richness (D) was relatively high (Irvine Bay = 1·5-3·08, Lynn of Lorne = 1·4-3·34) as was the species diversity (H′) (Irvine Bay = 1·17-1·97, Lynn of Lorne = 1·23-1·95). The proportional representation ($\text{J′}$) of each species within the community was greater in Irvine Bay ($\text{J′}$ = 0·57-0·77) than in the Lynn of Lorne ($\text{J′}$ = 0·50-0·72). Therefore these two communities of small demersal fish appeared to be similar at the community level but the way in which this was achieved was different.     

Empirical ocean-color algorithms to retrieve chlorophyll-a, total suspended matter, and colored dissolved organic matter absorption coefficient in the Yellow and East China Seas

A bio-optical dataset collected during the 1998?C2007 period in the Yellow and East China Seas (YECS) was used to provide alternative empirical ocean-color algorithms in the retrieval of chlorophyll-a (Chl-a), total suspended matter (TSM), and colored dissolved organic matter (CDOM) absorption coefficients at 440 nm (ag₄₄₀). Assuming that remote-sensing reflectance (Rrs) could be retrieved accurately, empirical algorithms for T_Chl (regionally tuned Tassan??s Chl-a algorithm) in case-1 waters (T_Chl2i in case-2 waters), T_TSM (regionally tuned Tassan??s TSM algorithm), and T_ag440 or C_ag440 (regionally tuned Tassan??s or Carder??s ag₄₄₀ algorithm) were able to retrieve Chl-a, TSM, and ag₄₄₀ with uncertainties as high as 35, 46, and 35%, respectively. Applying the standard SeaWiFS Rrs, T_Chl was not viable in the eastern part of the YECS, which was associated with an inaccurate SeaWiFS Rrs retrieval because of improper atmospheric correction. T_Chl behaved better than other algorithms in the turbid case-2 waters, although overestimation was still observed. To retrieve more reliable Chl-a estimates with standard SeaWiFS Rrs in turbid water (a proxy for case-2 waters), we modified T_Chl for data with SeaWiFS normalized water-leaving radiance at 555 nm (nLw₅₅₅) > 2 mW cm^?2 ??m^?1 sr^?1 (T_Chl2s). Finally, with standard SeaWiFS Rrs, we recommend switching algorithms from T_Chl2s (for case-2 waters) to MOC_Chl (SeaWiFS-modified NASA OC4v4 standard algorithm for case-1 waters) for retrieving Chl-a, which resulted in uncertainties as high as 49%. To retrieve TSM and ag₄₄₀ using SeaWiFS Rrs, we recommend empirical algorithms for T_TSM (pre-SeaWiFS-modified form) and MT_ag440 or MC_ag440 (SeaWiFS Rrs-modified forms of T_ag440 or C_ag440). These could retrieve with uncertainties as high as 82 and 52%, respectively.     

Chlorophyll distribution in continental shelf sediments off West Palm Beach,Florida and west end,Bahamas

Measurements were made of chlorophyll-a and phaeophytin-a in calcareous sediments along transects off the east coast of Florida (75–190 m) and the west coast of Grand Bahama Island (170–300 m). Solvent partitioning showed that chlorophyll-a concentrations never exceeded 0·1 mg m^?2 at either location, most as degradation products. Total pigment concentrations (chlorophyll and phaeopigments) ranged from 0·18–1·83 mg m^?2 in sediments off Grand Bahama Island and 2·50 to 20·65 mg m^?2 off West Palm Beach. Pigments, expressed per gram dry weight of sediments, increased with depth across the Florida Continental Shelf. This is probably due to differences in sediment character between near-shore and off-shore sediments.     

Variations in the boundary-drag coefficient in the tidal entrance to Chesapeake Bay,Virginia

Use of the quadratic shear-stress law for estimating boundary drag requires specific knowledge of the magnitude of a drag coefficient, C_D, and sectional mean velocity, $\text{u}\text{?}$. In previous attempts to adapt the relationship for use in studies of marine-sediment transport, the flow measurement has been standardized at a level 100 cm above the bed. The particularized value of the drag coefficient has been designated as C₁₀₀.In the entrance area to Chesapeake Bay, Virginia, C₁₀₀ has been found to range through unacceptably wide limits. Two-thirds of the values obtained are between 3.5 · 10^?3 and 5.4 · 10^?2. Mean C₁₀₀ for the area is 1.3 · 10^?2 as compared to 3 · 10^?3 for tidal channels within Puget Sound, Washington.Present data suggest that, given a moveable bed, a size hierarchy of mobile bed forms, time-varying flow, and a lack of equilibrium between flow and bed, C₁₀₀ changes continuously with boundary shear stress.Accurate evaluation of boundary shear stress in tidal entrances with high flow rates and mobile beds presently requires measurement of velocity profiles.