Populations In Coastal Waters Research Articles

Abundance of Heterotrophic Bacterial Population in Coastal Waters of Palghar Taluka, Maharashtra, India

The population density of total heterotrophic bacteria in coastal water at 4 different sites along Palghar taluka namely; Kelwa coast, Navapur coast, Dandi creek and Satpati coast were studied. Total heterotrophic bacterial count was found to range from 0.34×102 – 423.1× 102 CFUml-1 in coastal waters. Average heterotrophic bacterial abundance was noted higher during monsoon at all 4 sites in the study with 47.2× 102 ± 34.79 CFU ml1at Satpati coast, 281.55× 102 ± 148.45 CFU ml-1 at Dandi creek, 265.26× 102 ± 149.74 CFU ml-1 at Navapur coast, and 1.12 × 102 ± 0.54 CFU ml-1 at Kelwa coast. Dandi creek recorded highest bacterial count throughout study period irrespective of season.

Vertical distribution of bacteria populations at the finfish marine culture in North Bali Coast, Indonesia

One of the indicators of aquatic biology is the bacterial population. This study was conducted to determine the vertical distribution of bacterial populations in coastal waters at the marine fish farming in North Bali. Three locations of water samples in depths of 5, 10, 20, and 30 m samples were determined. They are shoreline near the hatcheries at Penyabangan and Gerokgak and water near the net cages at Pegametan Sumberkima. Three replications of the sample collection were done in the surface, middle, and bottom at each sampling point. Samples were collected monthly during the two seasonal transitions from April to June and August to October. The distribution of bacteria was determined by the culture-dependent method (CDM) by measuring the number of bacteria based on bacterial cultivability on agar media. The results showed a lower bacterial population (101-102 cfu/mL) was observed in August. An even distribution of total bacteria (103 cfu/mL) was seen at Pegametan Bay. Higher Vibrio spp. was found at a depth of 10 m than 20 and 30 m. While Pegametan Bay station had the highest Vibrio spp. number. Halotolerant bacteria tend to increase to 5 x 102 cfu/mL from April to June at a depth of 5.

Mitochondrial COI sequences revealed shallow but significant divergences among Amphioctopus aegina (Octopoda, Octopodidae) populations in coastal waters of China

Amphioctopus aegina is an important fishery resource in the coastal waters of China. In the present study, the genetic diversity and population genetic structure among four populations of A. aegina throughout its distributional range in China were assessed using the mitochondrial cytochrome oxidase 1 (COI) sequences. The results revealed a generally low genetic diversity (Hd: 0.2842–0.6670; Pi: 0.0007–0.0015) in A. aegina populations. The neighbor-joining (NJ) phylogenetic tree and the haplotype networks, as well as the results of the molecular variance (AMOVA) analyses, indicated a shallow phylogeographic structure among the four populations. However, pairwise ΦST statistics and genetic distance analyses revealed significant (p<0.01) genetic differentiation among Qinzhou and the rest three populations of Zhanjiang, Huizhou, and Dongshan. The demographic history analyses indicated a population expansion in A. aegina, and the role of Leizhou peninsula isolation in shaping the population differentiation. These results would largely enhance our understanding of the genetic structure and hence promote the scientific management of A. aegina fishery resources in coastal waters of China.

Jellyfish Bioprospecting in the Mediterranean Sea: Antioxidant and Lysozyme-Like Activities from Aurelia coerulea (Cnidaria, Scyphozoa) Extracts.

Marine invertebrates represent a vast, untapped source of bioactive compounds. Cnidarians are represented by nearly 10,000 species that contain a complex mixture of venoms, collagen, and other bioactive compounds, including enzymes, oligosaccharides, fatty acids, and lipophilic molecules. Due to their high abundance in coastal waters, several jellyfish taxa may be regarded as candidate targets for the discovery of novel lead molecules and biomaterials and as a potential source of food/feed ingredients. The moon jellyfish Aurelia coerulea is one of the most common jellyfish worldwide and is particularly abundant in sheltered coastal lagoons and marinas of the Mediterranean Sea, where it first appeared—as an alien species—in the last century, when Pacific oyster cultivation began. In the present study, the antioxidant and lysozyme antibacterial activities associated with extracts from different medusa compartments—namely the umbrella, oral arms, and secreted mucus—were investigated. Extracts from the oral arms of A. coerulea displayed significant antioxidant activity. Similarly, lysozyme-like activity was the highest in extracts from oral arms. These findings suggest that A. coerulea outbreaks may be used in the search for novel cytolytic and cytotoxic products against marine bacteria. The geographically wide occurrence and the seasonally high abundance of A. coerulea populations in coastal waters envisage and stimulate the search for biotechnological applications of jellyfish biomasses in the pharmaceutical, nutritional, and nutraceutical sectors.

MtDNA <italic>COⅠ</italic> sequence diversity of <italic>Gerres limbatus</italic> in coastal waters of China

In order to contribute information on genetic background of <italic>Gerres limbatus</italic> in coastal waters of China, 652 bp mtDNA <italic>COⅠ</italic> sequences of 140 individuals from 9 geographic populations were analyzed. 14 mutation sites were found and 13 haplotypes were identified, of which 9 were unique haplotypes and 4 were shared haplotypes. The overall haplotype and nucleotide diversity were low ( <italic>H</italic>_d=0.276±0.050, π =0.000 5±0.000 1 ), of which genetic diversity of populations from the east part of the Qiongzhou Strait ( <italic>H</italic>_d = 0.338-0.456, π = 0.000 6-0.001 1 ) was higher than those in the western Beibu Gulf ( <italic>H</italic>_d =0-0.295, π =0-0.000 5 ). Haplotype network diagrams did not show obvious genealogical and geographic structure. Genetic differentiation coefficicent(<italic>F</italic>_st) showed that there was indistinctively low-middle genetic differentiation between Naozhou population and other populations ( <italic>F</italic>_st= 0.0773-0.1696). No obvious differentiation was found among other populations ( <italic>F</italic>_st=-0.041 5-0.061 2). AMOVA analysis also showed that 95% population variation originated from within the group. The negative overall value of the neutrality test (Tajima’s <italic>D</italic>=-2.254 9; Fu’s <italic>F</italic>_s=-16.472 5 ) and a significant single peak in the nucleotide mismatch distribution were consistent with demographic expansion in the past, and deduced expansion time ranged from about 0.130 4 to 0.043 5 million years ago. Since the overall genetic diversity of the population was less than 0.5 and nucleotide diversity was less than 0.005, it was speculated that <italic>Gerres limbatus</italic> population in coastal waters of China had recently encountered a severe bottleneck effect. The nucleotide diversity of the Ningde and Naozhou populations was relatively high and had a conservation priority. As genetic diversity of populations in the Beibu Gulf was extremely low, measures should be taken to avoid further decline in genetic diversity.

Damage or benefit? How future scenarios of climate change may affect the distribution of small pelagic fishes in the coastal seas of the Americas

Species occurrence and distribution have already been directly affected by climate change, a scenario that is likely to be accentuated as the temperature rise is expected to exceed 2 °C by 2100. Owing to climate change, organisms are forced to migrate or adapt to new climatic conditions, and if they fail to do so, they are at risk of declining and becoming extinct. However, some species are adapted to overcome and even benefit from these new conditions, increasing their occurrence area or even their abundance. Using Bayesian Species Distribution Models (B-SDMs), we evaluated the current distribution of two halfbeak fishes, Hyporhamphus unifasciatus and Hemiramphus brasiliensis, and the effect of climate changes predicted for 2050 and 2100 on the distribution of these populations in coastal waters of the Americas. We used species occurrence data from bibliographical sources and online databases. One biotic (net primary production - NPP) and four abiotic variables (sea surface temperature - SST), sea surface salinity - SSS), depth, and sea bottom rugosity) were used as potential predictors of species distribution. Results indicated that both species are more likely found in shallower, warmer, and saltier waters. Model prediction suggests that they will probably benefit from climate change, with potential increase in their occurrence area in coastal regions of the Americas, especially due to temperature rise and increased salinity.

Distribution of Soft Coral Octocorallia (Alcyonacea) in coastal waters of Gonda, Polewali-Mandar, West Sulawesi

The research on “Distribution of Soft Coral Octocorallia: Alcyonacea population in coastal waters of Gonda, Polewali-Mandar, West Sulawesi” has been done from August to December 2017. This study aims to determine the soft coral distribution and diversity at different depths in Coastal waters of Gonda, Polewali-Mandar, West Sulawesi. The data collection was performed by using the “Line Intercept Transect (LIT)” method with 50 meters transect at a depth of 3 meters and 10 meters at each station. The transect line was following the contour lines. Sample identification was performed by means of video recording. Environmental parameters including temperature, salinity, dissolved oxygen, current, brightness, turbidity, and pH was measured during field campaign, respectively. Data analysis was done by using the Shannon-Wiener Diversity Index, Uniformity index, Dominance index and Morisita Index. The results showed that 16 species from four families of Soft Coral has been found in Gonda Beach, where the number of species found at 10m depth are higher than 3m depth, respectively. The average value of the diversity index at 3m depth (1.62) is higher than at 10m depth (1.34), but both are still classified in the moderate category. The pattern of population distribution in the overall site at this location tends to be random.

Shifting Winds Drive Ocean Temps Along South African Coast

A new study could help manage sardine populations in coastal waters.

Demography and genetics suggest reversal of dolphin source‐sink dynamics, with implications for conservation

AbstractThe forecast for the viability of populations depends upon metapopulation dynamics: the combination of reproduction and mortality within populations, as well as dispersal between populations. This study focuses on an Indo‐Pacific bottlenose dolphin (Tursiops aduncus) population in coastal waters near Bunbury, Western Australia. Demographic modeling of this population suggested that recent reproductive output was not sufficient to offset mortality. Migrants from adjacent populations might make up this deficit, so that Bunbury would act as a “sink,” or net recipient population. We investigated historical dispersal in and out of Bunbury, using microsatellites and mitochondrial DNA of 193 dolphins across five study locations along the southwestern Australian coastline. Our results indicated limited gene flow between Bunbury and adjacent populations. The data also revealed a net‐dispersal from Bunbury to neighboring populations, with microsatellites showing that more than twice as many individuals per generation dispersed out of Bunbury than into Bunbury. Therefore, in historic times, Bunbury appears to have acted as a source population, supporting nearby populations. In combination with the prior finding that Bunbury is currently not producing surplus offspring to support adjacent populations, this potential reversal of source‐sink dynamics may have serious conservation implications for Bunbury and other populations nearby.

Transcriptome analysis deciphers evolutionary mechanisms underlying genetic differentiation between coastal and offshore anchovy populations in the Bay of Biscay

Morphometry and otolith microchemistry point to the existence of two populations of the European anchovy (Engraulis encrasicolus) in the Bay of Biscay: one in open seawaters, and a yet unidentified population in coastal waters. To test this hypothesis, we assembled a large number of samples from the region, including 587 juveniles and spawning adults from offshore and coastal waters, and 264 fish from other locations covering most of the species’ European range. These samples were genotyped for 456 exonic SNPs that provide a robust way to decipher adaptive processes in these populations. Two genetically differentiated populations of anchovy inhabit the Bay of Biscay with different population dynamics: (1) a large offshore population associated with marine waters included in the wide-shelf group, and (2) a coastal metapopulation adapted to estuarine environments in the Bay of Biscay and North Sea included in the narrow-shelf group. Transcriptome analysis identified neutral and adaptive evolutionary processes underlying differentiation between these populations. Reduced gene flow between offshore and coastal populations in the Bay of Biscay appears to result from divergence between two previously isolated gene pools adapted to contrasting habitats and now in secondary contact. Eleven molecular markers appear to mark divergent selection between the ecotypes, and a majority of these markers are associated with salinity variability. Ecotype differences at two outlier genes, TSSK6 and basigin, may hinder gamete compatibility between the ecotypes and reinforce reproductive isolation. Additionally, possible convergent evolution between offshore and coastal populations in the Bay of Biscay has been detected for the syntaxin1B-otoferlin gene system, which is involved in the control of larval buoyancy. Further study of exonic markers opens the possibility of understanding the mechanisms of adaptive divergence between European anchovy populations.

Environmental factors and seasonal dynamics of Prorocentrum lima population in coastal waters of the Gulf of Tunis, South Mediterranean.

In the frame of a phytoplankton study, a series of samples were collected in the Punic harbors of Carthage (Gulf of Tunis, South Mediterranean) from March 2008 to March 2010. Species composition, seasonal variations of pelagic Prorocentrum populations and several physico-chemical parameters were specified, as well as the relation between Prorocentrum species dynamics and water temperature, salinity and nutrient concentrations. The main detected species are included in the benthic/epiphytic group; P. lima (Ehrenberg) Stein 1878 and P. emarginatum Fukuyo 1981. P lima was the dominant species. The highest abundance of P. lima (6.97 x 10(3) Cells L(-1)) was recorded in August 2008 where temperature and salinity values ranged from 23.1 to 30.2 degrees C and 36.1 to 40.3 psu, respectively. The dynamics of the P. lima population had significant positive correlations with both temperature and salinity, and negative correlations with both nitrogen/phosphorus ratio and ammonium concentrations. Proliferations of this species represent a serious hazard for public health in Tunis northern coasts.

Independence of neutral and adaptive divergence in a low dispersal marine mollusc

Identifying how the interplay between neutral and adaptive evolutionary processes shapes the spatial structure of natural populations is a central task in ecology and conservation biology. In marine populations, generally characterised by large population sizes and high gene flow, the simultaneous use of multiple descriptors (i.e. genetic, morphological, life-history, etc.) can be particularly helpful in unravelling the often subtle and complex spatial patterns observed. The gastropod Buccinum undatum (common whelk) lacks a planktonic larval stage, which could promote isolation of local populations and lead to phenotypic divergence through genetic drift or local adaptation. Despite the commercial significance of this species, the relative importance of these 2 forces remains unknown. Here, we used microsatellites, geometric morphometrics and shell thickness measurements to investigate the evolutionary dynamics generating spatial variation in 10 whelk populations in coastal waters around Ireland. Genetic diversity was generally high and genetic structure moderate but significant (overall FST = 0.019), in accordance with an isolation-by-distance pattern. Phenotypic divergence, as measured by PST, was uncorrelated with, and much more pronounced than, neutral divergence (FST), indicating that environmental variation rather than population isolation drives phenotypic differentiation. For some traits, at least, diversifying selection is likely to be involved unless additive genetic components of phenotypic variation among populations are very low. Our results document a lack of correspondence between neutral and adaptive divergence, and highlight the need to couple connectivity estimates with the assessment of ecologically relevant traits in fisheries management and conservation.

Population structure of island‐associated dolphins: Evidence from mitochondrial and microsatellite markers for common bottlenose dolphins (Tursiops truncatus) around the main Hawaiian Islands

AbstractWe used mitochondrial and nuclear genetic markers to investigate population structure of common bottlenose dolphins, Tursiops truncatus, around the main Hawaiian Islands. Though broadly distributed throughout the world's oceans, bottlenose dolphins are known to form small populations in coastal waters. Recent photo‐identification data suggest the same is true in Hawaiian waters. We found genetic differentiation among (mtDNA ΦST= 0.014–0.141, microsatellite F’ST= 0.019–0.050) and low dispersal rates between (0.17–5.77 dispersers per generation) the main Hawaiian Island groups. Our results are consistent with movement rates estimated from photo‐identification data and suggest that each island group supports a demographically independent population. Inclusion in our analyses of samples collected near Palmyra Atoll provided evidence that the Hawaiian Islands are also occasionally visited by members of a genetically distinct, pelagic population. Two of our samples exhibited evidence of partial ancestry from Indo‐Pacific bottlenose dolphins (T. aduncus), a species not known to inhabit the Hawaiian Archipelago. Our findings have important implications for the management of Hawaiian bottlenose dolphins and raise concerns about the vulnerability to human impacts of pelagic species in island ecosystems.

The role of acoustics in defining killer whale populations and societies in the Northeastern Pacific Ocean.

Stable, culturally inherited repertoires of discrete pulsed calls are characteristic of the acoustic behavior of killer whales. Call repertoires may have important roles in the evolution of social segregation and reproductive isolation of sympatric killer whale populations. Here we present the results of analyzes of recordings collected from killer whale populations in coastal waters of the Northeastern Pacific from the Aleutian Islands to the Gulf of California over the past 30 years. At least three acoustically, genetically, and ecologically distinct lineages of killer whales, known as residents, transients, and offshores, inhabit these waters. Call repertoires within these lineages can further distinguish populations, communities, or smaller social groups, depending on social structure and patterns of dispersal. Salmon-feeding residents live permanently in their natal matrilines and have group-specific dialects that encode maternal genealogy. Mammal-feeding transient groups have less stable societies and tend not to have group-specific dialects, though there are regional call differences among subpopulations. Offshore killer whales, which range widely along the continental shelf and may specialize on sharks, have distinct call repertoires that appear to vary among groups. Killer whale calls can provide important insights into the structure of populations at a scale that cannot be resolved through genetic studies.

A robust baseline for bottlenose dolphin abundance in coastal Moreton Bay: a large carnivore living in a region of escalating anthropogenic impacts

Marine megafauna populations in coastal waters are increasingly threatened by anthropogenic impacts. Moreton Bay, a large embayment in south-east Queensland, lies adjacent to one of the fastest growing regions in Australia and has a resident population of bottlenose dolphins, Tursiops aduncus. Evaluation of the effectiveness of any proposed management strategy requires robust population abundance estimates. We estimated abundances of bottlenose dolphins in central eastern Moreton Bay (350 km2) using two commonly used abundance estimation methods for cetaceans: photo-identification mark–recapture and line-transect surveys. Mark–recapture data were analysed in CAPTURE using a model that allowed capture probabilities to vary between sampling events and between individuals. Based on an estimated 76% of the population identifiable photographically, total abundance estimates were 673 ± 130 s.e. (1997) and 818 ± 152 s.e. (1998). Line-transect data, analysed using DISTANCE, gave an abundance estimate of 407 ± 113.5 s.e. (2000). These abundance estimates are large compared with many other coastal bottlenose dolphin populations. The line-transect surveys comprised a pilot study, and the lower line-transect abundance estimate is probably best attributable to methodological issues. In particular, smaller mean group size was estimated for the line-transects surveys (2.85 ± 0.29 s.e.) than the mark–recapture surveys (4.87 ± 0.39 s.e., 1997; 5.78 ± 0.73 s.e., 1998), and line-transect group sizes were probably underestimated. In addition, the line-transect detection probability (g(o)) was assumed to be one but was almost certainly less than one. However, the possibility of an actual decline in population size cannot be ruled out. Coefficients of variation (CV) were lower for mark–recapture than for line-transect surveys, however, CVs of line-transect estimates could be lowered through improved survey design. We evaluated the power of these surveys to detect trends in potential population declines for bottlenose dolphins in Moreton Bay and make recommendations for ongoing monitoring strategies.

Anthropogenic causes of jellyfish blooms and their direct consequences for humans: a review

Although recent articles state that jellyfish populations are increasing, most available evidence shows that jellyfish abundances fluctuate with climatic cycles. Reports of increasing prob- lems with jellyfish, especially in East Asia, are too recent to exclude decadal climate cycles. Jellyfish are infamous for their direct negative effects on human enterprise; specifically, they interfere with tourism by stinging swimmers, fishing by clogging nets, aquaculture by killing fish in net-pens and power plants by clogging cooling-water intake screens. They also have indirect effects on fisheries by feeding on zooplankton and ichthyoplankton, and, therefore, are predators and potential competitors of fish. Ironically, many human activities may contribute to increases in jellyfish populations in coastal waters. Increased jellyfish and ctenophore populations often are associated with warming caused by climate changes and possibly power plant thermal effluents. Jellyfish may benefit from eutrophication, which can increase small-zooplankton abundance, turbidity and hypoxia, all conditions that may favor jellyfish over fish. Fishing activities can remove predators of jellyfish and zooplanktivorous fish com- petitors as well as cause large-scale ecosystem changes that improve conditions for jellyfish. Aquacul- ture releases millions of jellyfish into Asian coastal waters yearly to enhance the jellyfish fishery. Aquaculture and other marine structures provide favorable habitat for the benthic stages of jellyfish. Changes in the hydrological regime due to dams and other construction can change the salinity to favor jellyfish. Accidental introductions of non-native gelatinous species into disturbed ecosystems have led to blooms with serious consequences. In many coastal areas, most of these environmental changes occur simultaneously. We summarize cases of problem jellyfish blooms and the evidence for anthropogenic habitat disruptions that may have caused them. Rapid development in East Asia makes that region especially vulnerable to escalating problems. We conclude that human effects on coastal environments are certain to increase, and jellyfish blooms may increase as a consequence.

Periodicity in the accumulation of gelatinous zooplankton during the summer season in the coastal area of Iyo‐Nada, Japan

Gelatinous zooplankton collected and quantified daily at the sluice gate of the Ikata Nuclear Power Station along the coast of Iyo‐Nada in the Seto Inland Sea were analyzed for the period 1998‐2004 in an effort to correlate the number of these animals with the physical oceanographic conditions. Sudden periodic and nonperiodic increases of gelatinous zooplankton occur repeatedly from early summer to late autumn in nearshore areas. Periodic increases are synchronous with the spring tidal period. Nearshore tide‐induced eddy development may play an important role for the aggregation process of gelatinous zooplankton, and the spring‐neap tidal variation of the circulation induces increases of the gelatinous zooplankton population in coastal waters of the Iyo‐Nada. Nonperiodic increases are attributable to typhoons and other storms. The strong shoreward currents due to the winds caused by these events transport gelatinous zooplankton to nearshore areas.

Low Levels of Environmental Ammonia Increase Susceptibility to Disease in Chinook Salmon Smolts

Ammonia criteria are established using data from standardized toxicity tests involving healthy animals. Both intrinsic and extrinsic environmental changes affect the immune system, but few toxicity studies consider the overall impact on this system and potential changes in resistance to infection. To investigate the effects of subacute levels of ammonia in coastal waters on physiological and immunological systems of fish, juvenile Chinook salmon were maintained in seawater (10 degrees C, pH 7.8) and exposed to two concentrations of ammonia, 2.5 and 10 mg/L total nitrogen. Both test levels resulted in increased internal levels of ammonia in the fish. Neither treatment level affected feeding rates. Over a time course of 10 d, numerous significant effects were observed. White blood cell counts changed significantly, as did respiratory burst activity, plasma lysozyme activity, and plasma glucose concentration in both treatments compared to controls. In an experimental infection with Vibrio anguillarum, fish previously exposed to subacute levels of ammonia were more susceptible to pathogenic challenge. The findings of this study indicate that a more thorough investigation into the effects of environmental ammonia on fish populations in coastal waters should be undertaken and the current environmental standards reassessed.

海底泥からの有鐘繊毛虫類の出現にかかわる温度と明暗条件の影響

Tintinnids survive conditions unsuitable for growth by forming cysts which are deposited in bottom sediments. Various environmental factors may influence their excystment. In this study, the effects of temperature and light on tintinnid excystment from marine sediments were examined by incubating the sediment samples in filtered seawater at different temperatures. Tintinnid excystment was initiated on Day 1 at 15, 20, and 25°C or on Day 2 at 10°C. At the higher temperatures, the number of excystments rapidly reached the maximum and the cumu-lative number of excystments during the first 5 days was greater than at the lower temperatures. Dark conditions suppressed tintinnid excystment., Dependence of excystment on temperature was different for different species. The range of temperature suitable for excystment of each species coincided with the range of water temperature above the bottom during the period when the respective species was abundant in nature. These results imply that excystment plays an important role in increasing tintinnid populations in coastal waters.

Phytoplankton biomass, production and growth limitations on the Huanghe (Yellow River) continental shelf

We examined phytoplankton populations in coastal waters of the Huanghe (Yellow River) estuary during two cruises in the annual high and normal discharge periods: August 1986 and October 1987, respectively. Strong salinity, nutrient, and phytoplankton pigment concentration gradients occur along the 5 m isobath. Landward of these gradients the phytoplankton growth potential (PGP) appears strongly phosphorus-limited and light limitation of PGP, paradoxically, appears less significant than it does further offshore where the euphotic zone depth is greater. Phytoplankton pigments are sparse both in the river and far offshore, and the peak accumulation (9 μg l −1 chlorophyll a) is centered broadly between 20 and 25 ppt, thus straddling the region of the hypopycnal plume from the hyperpycnal plunge point to where Secchi disk depth exceeds 1 m. As the suspended matter falls out (sharply) near the 25 ppt isohaline, light conditions improve, the N:P ratio drops to below 100, and nitrate concentrations continue to decrease in an offshore direction. Phytoplankton production rates reach a maximum and large algal cells accumulate where the suspended particulate matter concentration drops to less than 10 mg l −1. Both phytoplankton biomass and production declines beyond approximately 32 ppt. Sedimentary pigment accumulations also increase going from land to sea. Phosphorus and nitrogen dominate the suite of nutrients tested to determine which nutrients limit PGP. Phosphorus is probably the major nutrient limiting phytoplankton growth (not necessarily biomass accumulation) in most of the Huanghe estuary. This conclusion is based on the very high N:P ratios of dissolved nutrients, the results of an extensive array of addition and deletion bioassay experiments, and the results of P addition experiments. Where trace metals and EDTA limit PGP, they are usually limiting in concert with other nutrients and do not act alone. Comparison with other large river plumes are made.