Harrison
Paul J.
Harrison
Paul J.
No Thumbnail Available
Search Results
Now showing
1 - 5 of 5
-
PreprintTemporal and spatial variations in nutrient stoichiometry and regulation of phytoplankton biomass in Hong Kong waters : influence of the Pearl River outflow and sewage inputs( 2008-01) Xu, Jie ; Ho, Alvin Y. T. ; Yin, Kedong ; Yuan, Xiangcheng ; Anderson, Donald M. ; Lee, Joseph H. W. ; Harrison, Paul J.In 2001, the Hong Kong government implemented the Harbor Area Treatment Scheme (HATS) under which 70% of the sewage that had been formerly discharged into Victoria Harbor is now collected and sent to Stonecutters Island Sewage Works where it receives chemically enhanced primary treatment (CEPT), and is then discharged into waters west of the Harbor. The relocation of the sewage discharge will possibly change the nutrient dynamics and phytoplankton biomass in this area. Therefore, there is a need to examine the factors that regulate phytoplankton growth in Hong Kong waters in order to understand future impacts. Based on a historic nutrient data set (1986-2001), a comparison of ambient nutrient ratios with the Redfield ratio (N:P:Si=16:1:16) showed clear spatial variations in the factors that regulate phytoplankton biomass along a west (estuary) to east (coastal/oceanic) transect through Hong Kong waters. Algal biomass was constrained by a combination of low light conditions, a rapid change in salinity, and strong turbulent mixing in western waters throughout the year. Potential stoichiometric Si limitation (up to 94% of the cases in winter) occurred in Victoria Harbor due to the contribution of sewage effluent with high N and P enrichment all year, except for summer when the frequency of stoichiometric Si limitation (48%) was the same as P, owing to the influence of the high Si in the Pearl River discharge. In the eastern waters, potential N limitation and N and P co-limitation occurred in autumn and winter respectively, because of the dominance of coastal/oceanic water with low nutrients and low N:P ratios. In contrast, potential Si limitation occurred in spring and a switch to potential N, P and Si limitation occurred in eastern waters in summer. In southern waters, there was a shift from P limitation (80%) in summer due to the influence of the N-rich Pearl River discharge, to N limitation (68%) in autumn, and to N and P co-limitation in winter due to the dominance of N-poor oceanic water from the oligotrophic South China Sea. Our results show clear temporal and spatial variations in the nutrient stoichiometry which indicates potential regulation of phytoplankton biomass in HK waters due to the combination of the seasonal exchange of the Pearl River discharge and oceanic water, sewage effluent inputs, and strong hydrodynamic mixing from SW monsoon winds in summer and the NE monsoon winds in winter.
-
PreprintA comparison of eutrophication impacts in two harbours in Hong Kong with different hydrodynamics( 2009-09-03) Xu, J. ; Yin, K. ; Liu, H. ; Lee, Joseph H. W. ; Anderson, Donald M. ; Ho, Alvin Y. T. ; Harrison, Paul J.Eutrophication impacts may vary spatially and temporally due to different physical processes. Using a 22-year time series data set (1986-2007), a comparison of eutrophication impacts between two eutrophic harbors, Victoria and Tolo Harbours, in Hong Kong with very different hydrodynamic conditions was conducted. In the highly-flushed Victoria Harbour (Victoria), the highest Chl a (13 μg L-1) occurred due to stratification in summer as a result of the input of the eutrophic Pearl River discharge, but the high flushing rate restricted nutrient utilization and the further accumulation of algal biomass. In other seasons, vertical mixing induced light limitation and horizontal dilution led to low Chl a (< 2 μg L-1) and no spring bloom. Few hypoxic events (DO < 2 mg L-1) occurred due to strong tidal mixing. Therefore, Victoria is resilient to nutrient enrichment. In contrast, in the weakly-flushed Tolo Harbour (Tolo), year long stratification, the long residence times and weak tidal currents favored algal growth, resulting in a spring diatom bloom and high Chl a (up to 30 μg L-1) all year and frequent hypoxic events in summer. Hence, Tolo is susceptible to nutrient enrichment and it responded to nutrient reduction since sewage treatment resulted in a 32-38% decrease in algal biomass in Tolo, but not in Victoria. A significant (11-22%) reduction in bottom DO in the both harbors after sewage treatment was due to a decrease in the organic loading from sewage treatment or the diversion.
-
ArticleSynthesis of iron fertilization experiments : from the Iron Age in the Age of Enlightenment(American Geophysical Union, 2005-09-28) Baar, Hein J. W. de ; Boyd, Philip W. ; Coale, Kenneth H. ; Landry, Michael R. ; Tsuda, Atsushi ; Assmy, Philipp ; Bakker, Dorothee C. E. ; Bozec, Yann ; Barber, Richard T. ; Brzezinski, Mark A. ; Buesseler, Ken O. ; Boye, Marie ; Croot, Peter L. ; Gervais, Frank ; Gorbunov, Maxim Y. ; Harrison, Paul J. ; Hiscock, William T. ; Laan, Patrick ; Lancelot, Christiane ; Law, Cliff S. ; Levasseur, Maurice ; Marchetti, Adrian ; Millero, Frank J. ; Nishioka, Jun ; Nojiri, Yukihiro ; van Oijen, Tim ; Riebesell, Ulf ; Rijkenberg, Micha J. A. ; Saito, Hiroaki ; Takeda, Shigenobu ; Timmermans, Klaas R. ; Veldhuis, Marcel J. W. ; Waite, Anya M. ; Wong, Chi-ShingComparison of eight iron experiments shows that maximum Chl a, the maximum DIC removal, and the overall DIC/Fe efficiency all scale inversely with depth of the wind mixed layer (WML) defining the light environment. Moreover, lateral patch dilution, sea surface irradiance, temperature, and grazing play additional roles. The Southern Ocean experiments were most influenced by very deep WMLs. In contrast, light conditions were most favorable during SEEDS and SERIES as well as during IronEx-2. The two extreme experiments, EisenEx and SEEDS, can be linked via EisenEx bottle incubations with shallower simulated WML depth. Large diatoms always benefit the most from Fe addition, where a remarkably small group of thriving diatom species is dominated by universal response of Pseudo-nitzschia spp. Significant response of these moderate (10–30 μm), medium (30–60 μm), and large (>60 μm) diatoms is consistent with growth physiology determined for single species in natural seawater. The minimum level of “dissolved” Fe (filtrate < 0.2 μm) maintained during an experiment determines the dominant diatom size class. However, this is further complicated by continuous transfer of original truly dissolved reduced Fe(II) into the colloidal pool, which may constitute some 75% of the “dissolved” pool. Depth integration of carbon inventory changes partly compensates the adverse effects of a deep WML due to its greater integration depths, decreasing the differences in responses between the eight experiments. About half of depth-integrated overall primary productivity is reflected in a decrease of DIC. The overall C/Fe efficiency of DIC uptake is DIC/Fe ∼ 5600 for all eight experiments. The increase of particulate organic carbon is about a quarter of the primary production, suggesting food web losses for the other three quarters. Replenishment of DIC by air/sea exchange tends to be a minor few percent of primary CO2 fixation but will continue well after observations have stopped. Export of carbon into deeper waters is difficult to assess and is until now firmly proven and quite modest in only two experiments.
-
PreprintOcean urea fertilization for carbon credits poses high ecological risks( 2008) Glibert, Patricia M. ; Azanza, Rhodora ; Burford, Michele ; Furuya, Ken ; Abal, Eva ; Al-Azri, Adnan ; Al-Yamani, Faiza ; Andersen, Per ; Anderson, Donald M. ; Beardall, John ; Berg, Gry M. ; Brand, Larry E. ; Bronk, Deborah ; Brookes, Justin ; Burkholder, JoAnn M. ; Cembella, Allan D. ; Cochlan, William P. ; Collier, Jackie L. ; Collos, Yves ; Diaz, Robert ; Doblin, Martina ; Drennen, Thomas ; Dyhrman, Sonya T. ; Fukuyo, Yasuwo ; Furnas, Miles ; Galloway, James ; Graneli, Edna ; Ha, Dao Viet ; Hallegraeff, Gustaaf M. ; Harrison, John A. ; Harrison, Paul J. ; Heil, Cynthia A. ; Heimann, Kirsten ; Howarth, Robert W. ; Jauzein, Cecile ; Kana, Austin A. ; Kana, Todd M. ; Kim, Hakgyoon ; Kudela, Raphael M. ; Legrand, Catherine ; Mallin, Michael ; Mulholland, Margaret R. ; Murray, Shauna A. ; O’Neil, Judith ; Pitcher, Grant C. ; Qi, Yuzao ; Rabalais, Nancy ; Raine, Robin ; Seitzinger, Sybil P. ; Salomon, Paulo S. ; Solomon, Caroline ; Stoecker, Diane K. ; Usup, Gires ; Wilson, Joanne ; Yin, Kedong ; Zhou, Mingjiang ; Zhu, MingyuanThe proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.
-
ArticleAnthropogenic nutrients and harmful algae in coastal waters(Elsevier, 2014-08-28) Davidson, Keith ; Gowen, Richard J. ; Harrison, Paul J. ; Fleming, Lora E. ; Hoagland, Porter ; Moschonas, GrigoriosHarmful algal blooms (HABs) are thought to be increasing in coastal waters worldwide. Anthropogenic nutrient enrichment has been proposed as a principal causative factor of this increase through elevated inorganic and/or organic nutrient concentrations and modified nutrient ratios. We assess: 1) the level of understanding of the link between the amount, form and ratio of anthropogenic nutrients and HABs; 2) the evidence for a link between anthropogenically generated HABs and negative impacts on human health; and 3) the economic implications of anthropogenic nutrient/HAB interactions. We demonstrate that an anthropogenic nutrient-HAB link is far from universal, and where it has been demonstrated, it is most frequently associated with high biomass rather than low biomass (biotoxin producing) HABs. While organic nutrients have been shown to support the growth of a range of HAB species, insufficient evidence exists to clearly establish if these nutrients specifically promote the growth of harmful species in preference to benign ones, or if/how they influence toxicity of harmful species. We conclude that the role of anthropogenic nutrients in promoting HABs is site-specific, with hydrodynamic processes often determining whether blooms occur. We also find a lack of evidence of widespread significant adverse health impacts from anthropogenic nutrient-generated HABs, although this may be partly due to a lack of human/animal health and HAB monitoring. Detailed economic evaluation and cost/benefit analysis of the impact of anthropogenically generated HABs, or nutrient reduction schemes to alleviate them, is also frequently lacking.