Harmful algal bloom species and phosphate-processing effluent: field and laboratory studies

In 2002, the Florida Department of Environmental Protection began discharging phosphate-processing effluent into Bishop Harbor, an estuary within Tampa Bay. Because of concerns that the effluent would serve as a nutrient source for blooms of the toxic dinoflagellate Karenia brevis, a field monitoring program was established and laboratory bioassays were conducted. Several harmful algal bloom (HAB) species, including Prorocentrum minimum and Heterosigma akashiwo, were observed in bloom concentrations adjacent to the effluent discharge site. Blooms of diatoms were widespread throughout Bishop Harbor. K. brevis was observed with cell concentrations decreasing with increasing proximity to the effluent discharge site. Bioassays using effluent as a nutrient source for K. brevis resulted in decreased cell yields, increased growth rates, and increased time to log-phase growth. The responses of HAB species within Bishop Harbor and of K. brevis to effluent in bioassays suggested that HAB species differ in their response to phosphate-processing effluent.     

城市湖泊春季绿藻水华特征及其影响因素——以宁波月湖为例

城市湖泊富营养化问题日趋严峻,以往对水华的研究多集中于大型自然淡水湖库,而对小型城市浅水湖泊的水华动态相对较少.以宁波月湖为研究对象,探讨水华暴发期间浮游植物变化特征及与影响因子之间的关系,以期判别影响城市湖泊水华的主控因子.月湖水华期间营养盐水平处于中富营养至极端富营养之间,此次共检出浮游植物8门61属,藻种组成以绿藻门（51.79%）和硅藻门（21.43%）为主,各点位浮游植物生长主要受水温、光照驱动,经历了隐藻门→硅藻门→绿藻门→蓝藻门的演替.水华种为雷氏衣藻（Chlamydomonas reinhardtii）,总藻密度最高达到1.55×10⁸ cells/L,水华暴发后各点位衣藻属比例升高（最高达到81.10%）,群落结构呈现单一化特征.通过Pearson相关性分析和RDA分析发现衣藻属生长与水温、pH、总磷浓度均呈显著正相关,春季气温回升、天气持续晴好,城市浅水湖泊高营养盐负荷、水体流动性差等特点为带鞭毛的衣藻属提供了适宜的生存条件,在环境条件均适宜的情况下拥有最大生长潜力的衣藻属在营养盐、光照等竞争中生长速率明显优于其他藻种,从而发生绿藻水华.     

Modeling spring-summer phytoplankton bloom in Lake Michigan with and without riverine nutrient loading

There were two phytoplankton blooms captured by remote sensing in Lake Michigan in 1998, one from March to May, and one during June. In this paper, those phytoplankton blooms were simulated by a coupled physical–biological model, driven by observed meteorological forcing in 1998. The model reasonably reproduced the lake currents. The biological model results, with and without riverine nutrient loading, were compared with the remote sensing data. A 3-month-long donut-like phytoplankton bloom that appeared in southern Lake Michigan was reasonably well simulated only when riverine input was included, indicating the importance of riverine nutrient input for supporting the growth of phytoplankton in Lake Michigan. The model with riverine input also captured a second event-driven phytoplankton bloom during June with weaker magnitude that occurred in mid-south Lake Michigan, which lasted for about 20 days. The major reason for the weaker bloom in June was that vertical mixing in the hydrodynamic model was too weak (leading to a mixed-layer depth of 20 m) to bring the bottom nutrient-rich water up to the epilimnion. High chlorophyll concentration that persisted in Green Bay for almost a year was simulated with less intensity.     

Harmful algal blooms (HABs) in Daya Bay, China: An in situ study of primary production and environmental impacts

A month-long investigation of phytoplankton biomass and primary production (PP) was carried out during a harmful algal bloom (HAB) in Daya Bay, China, in 2003. During the bloom, the phytoplankton community was dominated by Scrippsiella trochoidea and Chattonella marina. The phytoplankton biomass (Chl a) and PP reached peak levels of 519.21 mg m⁻³ and 734.0 mgC m⁻³ h⁻¹, respectively. Micro-phytoplankton was the key contributor to Chl a and PP in a cage-culture area and in the adjacent HAB-affected waters, with percentages of up to 82.91% and 84.94%, respectively. The HAB had complicated relationships with hydrological and meteorological factors in Daya Bay. However, the water around the cage-culture area always showed statistically greater phytoplankton biomass and nutrient loadings than in adjacent waters, suggesting that this was the “trigger area” of the bloom. The spatial and temporal distribution of diverse HABs in Daya Bay, their ecological characteristics, and their environmental impacts are also discussed in this paper.     

细菌群落组成对微囊藻水华分解过程的响应

为探究细菌群落组成对微囊藻水华腐败分解过程的响应,在太湖梅梁湾沿岸进行为期11 d的原位围隔实验,模拟蓝藻水华聚集分解过程,并监测了此过程中水体环境因子和细菌群落组成.结果表明,水体理化因子和细菌群落组成在微囊藻水华分解的过程中发生了显著变化.冗余分析显示细菌的群落组成与水体氧化还原环境(溶解氧或氧化还原电位)、pH值、浮游植物生物量和营养盐浓度(总磷、硝态氮浓度)密切相关.研究还发现了某些与微囊藻水华分解密切相关的特殊细菌类群,其中隶属于黄杆菌科(拟杆菌门)的一个类群在微囊藻厌氧分解的阶段占据显著优势,其功能有待于进一步研究.     

Spring and summer blooms of phytoplankton (SeaWiFS/MODIS) along a ferry line in the Bay of Biscay and western English Channel

The seasonal cycle of chlorophyll concentration in the Bay of Biscay and western English Channel has been examined using satellite data (chlorophyll, sea surface temperature (SST), photosynthetically available radiation (PAR) and wind) along the line of the ferry Pride of Bilbao (Bilbao to Portsmouth). The spring phytoplankton bloom develops regularly in the oceanic region of the Bay of Biscay from mid March to the beginning of May with peak chlorophyll concentrations ranging 2–4 mg m^?3. Low wind turbulence is a major factor allowing the development of productivity pulses in the Bay of Biscay during spring. Exceptional blooms of phytoplankton take place in summer (July–August) in the western English Channel with chlorophyll concentrations as high as 40 mg m^?3. Some environmental factors (SST, wind, pressure and tide) are examined. Autumn blooms of phytoplankton (1–2 mg m^?3) are also detected in the northern Bay of Biscay, shelf-break and Celtic Sea in October. A 11 years pluri-annual synthesis of SeaWiFS satellite measurements is presented.     

The growth dynamics of Karenia brevis within discrete blooms on the West Florida Shelf

As part of the ECOHAB: Florida Program, we studied three large blooms of the harmful bloom forming dinoflagellate Karenia brevis. These blooms formed on the West Florida Shelf during Fall of 2000 off Panama City, and during Fall 2001 and Fall 2002 off the coastline between Tampa Bay and Charlotte Harbor. We suggest that these blooms represent two different stages of development, with the 2000 and 2001 blooms in an active growth or maintenance phase and the 2002 bloom in the early bloom initiation phase. Each bloom was highly productive with vertically integrated primary production values of 0.47–0.61, 0.39–1.33 and 0.65 g C m⁻² d⁻¹ for the 2000, 2001 and 2002 K. brevis blooms, respectively. Carbon specific growth rates were low during each of these blooms with values remaining fairly uniform with depth corresponding to generation times of 3–5 days. Nitrogen assimilation by K. brevis was highest during 2001 with values ranging from 0.15 to 2.14 μmol N L⁻¹ d⁻¹ and lower generally for 2000 and 2002 (0.01–0.64 and 0.66–0.76 μmol N L⁻¹ d⁻¹ for 2000 and 2002, respectively). The highest K. brevis cell densities occurred during the 2001 bloom and ranged from 400 to 800 cells mL⁻¹. Cell densities were lower for each of the 2000 and 2002 blooms relative to those for 2001 with densities ranging from 100 to 500 cells mL⁻¹. The 2000 and 2001 blooms were dominated by K. brevis in terms of its contribution to the total chlorophyll a (chl a) pool with K. brevis accounting generally for >70% of the observed chl a. For those populations that were dominated by K. brevis (e.g. 2000 and 2001), phytoplankton C biomass (C_p,0) constituted <30% of the total particulate organic carbon (POC). However, in 2002 when diatoms and K. brevis each contributed about the same to the total chl a, C_p,0 was >72% of the POC. The fraction of the total chl a that could be attributed to K. brevis was most highly correlated with POC, chl a and salinity. Nitrogen assimilation rate and primary production were highly correlated with a greater correlation coefficient than all other comparisons.     

Community structure in boreal lakes with recurring blooms of the nuisance flagellate Gonyostomum semen

Blooms of the nontoxic raphidophyte Gonyostomum semen have shown a recent increase in frequency and distribution in the Fennoscandian region. Due to large cell size and several grazer-avoidance strategies, G. semen is hypothesized to be inedible for most zooplankton species and therefore may constitute a bottleneck for the transfer of energy and nutrients in pelagic food webs. Repression of other phytoplankton through increased competition and induced mortality could further exacerbate this effect. In a field study of four lakes with recurring blooms of G. semen and four lakes without blooms, we found significant differences in community structure between the two lake groups during the bloom period. Bloom-lakes had lower biovolumes of small chrysophytes and chlorophytes and zooplankton assemblages were predominated by small, potentially bacterivorous cladocerans, suggesting a limited availability of edible phytoplankton and an increased importance of microbial pathways during G. semen blooms. Low biovolumes of large cladocerans in bloom-lakes may be due to interference of G. semen with filter feeding. Moreover, high abundances of the phantom midge Chaoborus flavicans in bloom-lakes suggest that the flow of energy and nutrients is directed more towards this invertebrate predator than fish. This could have negative impacts on fish populations, especially if bloom periods are prolonged.     

Phytoplankton diversity and chlorophyll-A in a polluted estuary

The quantity of phytoplankton in Newark Bay, New Jersey as indicated by chlorophyll-a content of the water, is low in the winter and early spring, and fluctuates greatly during the spring and summer. Chlorophyll-a concentrations are generally less than 20 μg/l until April. Between April and August, three phytoplankton blooms were indicated by chlorophyll-a concentrations as high as 81.4 μg/l. Net phytoplankton diversity values indicated generally eutrophic conditions; however, there was no significant correlation between diversity and chlorophyll-a concentrations. A role of nannoplankton in blooms is indicated.     

Phytoplankton response to short-term temperature and nutrient changes

Meteorological extreme events (heavy rainfall, heat waves) may lead to fast changes in nutrient load and water temperature in temperate lakes. We conducted laboratory experiments with an artificial phytoplankton community to mimic a rapid temperature increase (from 21 °C to 29 °C) at low nutrient levels (‘heat wave scenario’), respectively temperature decrease (from 21 °C to 16 °C) and increased nutrient load (‘heavy rainfall scenario’). We hypothesised that there is a taxon specific nutrient x temperature interaction, leading to significant shifts in the phytoplankton community composition when both variables change. To separate the temperature effect from the nutrient effect, we performed another experimental series at a reduced temperature but without addition of nutrients. As expected, the nutrient effect was overall more important than temperature and significantly affected all five taxa tested that represented different algal classes. However, temperature also played an important role for community composition, because the cryptophyte Cryptomonas sp. and the dinoflagellate Peridinium sp. reached significantly higher biovolumes at lower temperatures. The nutrient x temperature interaction was significant in the green alga Scenedesmus obliquus. These findings suggest that our experimental results cannot be interpreted primarily by species competition for nutrients. Heterotrophic bacteria were present in all experiments. Bacterial biomass was significantly positively related to temperature and nutrients. However, relative to phytoplankton biovolume, bacterial biovolume decreased under nutrient replete conditions. In conclusion, our results demonstrate that short-term environmental change may significantly affect both the phytoplankton community (in terms of species dominance and total biomass) and the ratio between autotrophs and heterotrophs in temperate lakes.     

Phytoplankton dynamics and cyanobacterial dominance in Murchison Bay of Lake Victoria (Uganda) in relation to environmental conditions

Murchison Bay is a shallow embayment in the north-western part of Lake Victoria, strongly influenced by urban pollution from the Ugandan capital Kampala. Two stations, representing the semi-enclosed innermost part of the bay and the wider outer part of the bay, were sampled in the period from April 2003 to March 2004, in order to assess the phytoplankton community and the nutrient status in the bay. Murchison Bay was highly eutrophic with average concentrations (n=25) of total phosphorous >90 μg L⁻¹ and total nitrogen >1100 μg L⁻¹ in the inner part of the bay. The phytoplankton community was dominated by a variety of cyanobacterial species and diatoms. Cyanobacteria were dominant in the whole bay, whereas diatoms were more abundant in the outer part of the bay. Moreover, the proportion of N-fixing species like Anabaena sp. was higher in the outer part of the bay, whereas species like Microcystis sp. were more abundant in the inner part of the bay. The phytoplankton community, especially in the outer part of the bay, may be influenced by light limitation. Low NO₃-N concentrations in the bay may also indicate a possible N-limitation, thus favouring growth of N-fixing cyanobacteria. The open bay is, however, a complex system, and additional environmental factors and loss processes most likely affect the phytoplankton community.     

基于非线性时序分析的三峡支流浮游植物因果响应

水华的频发已成为当前三峡水库最为突出的生态环境问题之一。尽管水动力调控叠加上温度变暖和营养负荷增加会诱导水华暴发强度和频率增加,但仍缺乏有效的方法框架去利用野外观测数据评估环境因子与浮游植物间的因果关联。本研究以三峡水库澎溪河监测数据为例,采用非线性时序分析的建模框架来量化浮游植物的因果响应规律。数据来自于2007年6月至2018年9月澎溪河流域的高阳平湖和汉丰湖两个观测点,其中包含了水文、气象和水质及叶绿素a等11种变量。首先,利用奇异谱分析(SSA)分离了叶绿素a和环境因子的低维确定性动力学信号;其次,采用收敛交叉映射(CCM)方法检验了叶绿素a与环境因子间的因果关联。结果显示:(1)气象因子、支流流量、水温、三峡大坝水位和上游调节坝水位是影响高阳平湖叶绿素a时序变化的重要因素;(2)总氮、总磷为代表的营养盐只在汉丰湖观测点中表现出与叶绿素a的因果关系,且总氮较之于总磷对叶绿素a变化影响更为显著;(3)CCM结果与传统的皮尔森相关性分析及格兰杰因果检验比较,证实非线性时序分析方法在分析浮游植物的因果响应上更具优势。本研究为水生态系统的因果建模提供了研究范例,也为推动利用长期观测数据...     

Bloom forming and toxic phytoplankton in transitional and coastal waters of Cantabria region coast (Southeastern Bay of Biscay,Spain)

Phytoplankton monitoring has extended to practically all the regions of the European coast due to the implementation of the European Water Framework Directive. In this way, the study of phytoplankton taxonomic composition and dynamic is being performed in many areas poorly studied or not studied before. During the last years, a monitoring programme has been carried out at the coast of Cantabria region (SE Bay of Biscay); the presence of some potentially toxic and bloom forming species (>7.5 × 10⁵ cells per litre) has been observed. Diatoms and cryptophytes are the main blooming taxa in this region in the majority of the estuaries and in some of the coastal sites. All estuaries and coastal stations showed at least one potentially toxic species, being the dinoflagellates the group with the highest number of taxa observed. The potentially toxic species found in highest concentrations were the genera Pseudo-nitzschia and Chrysochromulina.     

Seasonal succession of cyanobacterial protease inhibitors and Daphnia magna genotypes in a eutrophic Swedish lake

Lakes are well known for having a pattern of seasonal succession of phytoplankton and zooplankton. The succession of different taxa of phytoplankton results in a succession of zooplankton taxa, and within the genus Daphnia, into a succession of different genotypes (clones). One cause for this succession of Daphnia clones might be the production of digestive protease inhibitors by cyanobacteria, which usually bloom in summer. Here we report seasonal changes in the frequency and the abundance of Daphnia magna haplotypes in a eutrophic lake, which developed a chymotrypsin-inhibitor-producing cyanobacterial bloom in May. These seasonal changes were not related to changes of biotic and abiotic lake parameters. However, a very high content of chymotrypsin inhibitors was observed in May (but not in other months). This was assumed to have exerted a strong punctual selection pressure on the Daphnia population and on the direct targets of the protease inhibitors, i.e. the digestive chymotrypsins of Daphnia. Actually, D. magna from before and during the cyanobacterial bloom showed a different protease pattern on activity stained SDS-PAGE in comparison to clones from the month after the bloom. However, no difference in tolerance, measured as IC₅₀ values, to inhibition by natural lake seston from May was found between the clones from before and after the bloom. Thus, the hypothesis that a seasonal adaptation of D. magna subpopulations from either April/May or June might have occurred could not be proven. This suggests that the Daphnia population investigated here is locally adapted to cyanobacterial protease inhibitors.     

三峡水库支流小江富营养化模型构建及在水量调度控藻中的应用

三峡水库蓄水以来,支流小江呈富营养化加重的趋势,且多次暴发春季水华.水库蓄水以后支流流速变缓,水体滞留时间增加,是引发支流水华的主要因素之一.基于MIKE软件,建立小江调节坝下游至河口的二维水动力-富营养化模型,考虑碳、氮、磷3种元素在浮游植物有机体、死亡腐屑和无机盐中的循环转化,模拟小江河段的春季水华过程.分析小江生态调节坝的水量调节抑藻作用,即人为制造"洪水脉冲",增加短时间内的水流流速,对下游流场进行扰动以控制水华.计算结果表明,增大泄水量对调节坝下游的小江河段的春季藻华总体上具有一定的抑制作用.小江上游河段调度作用效果明显,下游高阳至入汇口河段调节作用较小,上游调节坝水力调度可以作为三峡水库支流水华应急治理措施之一.营养盐控制应该是控制支流水华的根本措施.     

Species diversity of resident green algae slows the establishment and proliferation of the cyanobacterium Microcystis aeruginosa

As harmful algal blooms (HABs) have expanded in size and become more frequent, there have been increased efforts to predict when and why blooms occur, as well as to identify the ecological factors that limit their formation. Here we report the results of a laboratory experiment in which we examined how the establishment and proliferation of Microcystis aeruginosa, a common HAB species, was influenced by competition with resident green algae. We hypothesized that competition with green algae would reduce the final biomass of M. aeruginosa, and that the effects of competition would be most pronounced in communities of high species richness and when nutrients are scarce. We found that competition with green algae did, in fact, consistently reduce the final biomass of M. aeruginosa. The effects of competition were more pronounced in species-rich than in species-poor communities, but this was only true when nutrients were abundant. When nutrients were scarce, resident diversity did not matter because competition with any resident species was sufficient to limit the growth of M. aeruginosa. Our results confirm that biotic interactions with phytoplankton are important in limiting the establishment and proliferation of HAB species like M. aeruginosa. But our work goes on to suggest that, under some nutrient conditions, diverse communities of resident phytoplankton can be more resistant to proliferation of cyanobacteria that can cause HABs.     

Validation of SeaWiFS chlorophyll a in Massachusetts Bay

Massachusetts Bay, a semi-enclosed embayment (50×100 km) in the Northwest Atlantic, is the focus of a monitoring program designed to measure the effects of relocating the Boston Harbor sewage outfall to a site 15 km offshore in Massachusetts Bay. The Massachusetts Water Resources Authority (MWRA) in situ monitoring program samples selected stations up to 17 times per year to observe seasonal changes in phytoplankton biomass and other water quality variables. We investigated the feasibility of augmenting the monitoring data with satellite ocean color data to increase the spatial and temporal resolution of quantitative phytoplankton measurements. In coastal regions such as Massachusetts Bay, ocean color remote sensing can be complicated by in-water constituents whose concentrations vary independently of phytoplankton and by inaccurate modeling of absorbing aerosols that tend to be concentrated near the coast. An evaluation of in situ and sea-viewing wide field-of-view sensor (SeaWiFS) measurements from 1998 to 2005 demonstrated that SeaWiFS overestimated chlorophyll a mainly due to atmospheric correction errors that were amplified by absorption from elevated concentrations of chlorophyll a and colored dissolved organic matter. Negative water-leaving radiances in the 412 nm band, an obvious artifact of inadequate atmospheric correction, were recorded in approximately 60–80% of the cloud-free images along the coast, while the remaining portions of the Bay only experience negative radiances 35–55% of the time with a clear nearshore to offshore decrease in frequency. Seasonally, the greatest occurrences of negative 412 nm radiances were in November and December and the lowest were recorded during the summer months. Concentrations of suspended solids in Massachusetts Bay were low compared with other coastal regions and did not have a significant impact on SeaWiFS chlorophyll a measurements. A regional empirical algorithm was developed to correct the SeaWiFS data to agree with in situ observations. Monthly SeaWiFS composites illustrated the spatial extent of a bimodal seasonal pattern, including prominent spring and fall phytoplankton blooms; and the approximate 115 cloud-free scenes per year revealed interannual variations in the timing, magnitude and duration of phytoplankton blooms. Despite known artifacts of SeaWiFS in coastal regions, this study provided a viable chlorophyll a product in Massachusetts Bay that significantly increased the spatial and temporal synoptic coverage of phytoplankton biomass, which can be used to gain a comprehensive ecosystem-wide understanding of phytoplankton dynamics at event, seasonal and interannual timescales.     

Temporal variation of diatom benthic propagules in a monsoon-influenced tropical estuary

Temporal variations in the diatom benthic propagule (DBP) community and their role in the phytoplankton community in a monsoon-affected tropical estuary, Zuari estuary, Goa (India) are presented. The DBP from the sediments was enumerated using an extinction dilution method (most probable number method), which allows estimation of resting stages through examination of germinated vegetative cells in culture. The DBP community was dominated by planktonic species belonging to the genera Skeletonema, Fragilariopsis, Thalassiosira, and Chaetoceros. Benthic propagules (BPs) of Skeletonema costatum and Fragilariopsis sp. were dominant throughout the year. Between these two species, only S. costatum showed a linear relationship between the BP and planktonic cells, indicating that this species is particularly important in coupling of pelagic and benthic ecosystems. During the onset and restart of monsoon after an intermittent break, water column was stratified, with a low-salinity layer arising from riverine discharge and precipitation at the surface and relatively cold, saline, low-oxygen waters at the bottom. Stratification favored blooming of S. costatum and Fragilariopsis sp. in nutrient-rich surface and bottom waters, respectively. The decline in these blooms ensuing nitrate depletion and salinity change resulted in an increased abundance of BP. Chaetoceros bloom was observed during the monsoon break as well as during non-monsoon period and on both the occasions the decline in bloom was coupled with freshwater discharge. During the non-monsoon season, Thalassiosira blooms were encountered subsequent to high nitrate inputs. These findings suggest that in such shallow tropical regions, physical processes during monsoon (freshwater discharge) and non-monsoon seasons (currents, waves and tides) cause resuspension of diatom BP. Since light is not a limiting factor for germination in such regions, the blooming of resuspended BP depends on nutrient availability.     

三峡水库香溪河库湾拟多甲藻(Peridiniopsis)水华对环境中磷的响应机制

于2015年春季拟多甲藻水华暴发期在香溪河支流高岚河、南阳河与干流设置9个采样点,探讨浮游植物种群与水体总磷浓度等环境因子的相关性;同时,分离纯化拟多甲藻后,设置5个不同磷浓度(0、0.005、0.020、0.100、0.600 mg/L)对其进行实验室培养,分别测定其比生长速率;在对数生长期,检测不同磷浓度培养下的藻细胞的快速光曲线及其参数;检测不同磷浓度培养下的藻细胞对外源无机碳的吸收效率及其参数.结果表明,水体中总磷浓度越高的河段,拟多甲藻细胞密度越高;培养基中磷浓度越高,拟多甲藻的比生长速率越大,光合效率越高,其对外源无机碳的吸收能力越强.这些结果表明高磷的水环境可能是促使拟多甲藻形成水华的关键因素之一.