Impact of Land-Based Sources On Marine Environment: Phytoplankton Blooms Within an Annual Cycle

The discharge water into the western region of Alexandria (Egypt), creates suitable conditions for the acceleration of the phytoplankton growth; daily replenishment of nutrients and development of density stratified water column. Water transparency and ammonia concentrations seem to be affecting the variations of the numerical standing crop. Eight phytoplankton bloom pulses of different causative species were observed. Asterionella glacialis represents a newly recorded red tide species in the neritic waters of Alexandria.     

Ecological Study of Spring-Early Summer Phytoplankton Blooms in A Semi-Enclosed Estuary

A sampling station in the Eastern Harbour of Alexandria was operated for 51 days between 2 March and 12 June, 1991. the harbour had different wide physical and chemical variations. Six distinct phytoplankton blooms occurred during this period. It is concluded that the physicochemical conditions affected the phytoplankton community structure and species composition. A dense diatom bloom could be maintained in a very weak and/or stabilized water column. A diatom bloom does not necessarily accompany an enhanced nutrient period. the depletion of nutrients and establishment of thermal stratification probably created favourable conditions for dinoflagellate and flagellate species to achieve blooms. the species composition could be shifted over the short term and a dense phytoplankton bloom could possibly dissipate in a few days.     

Water Discoloration in Alexandria, Egypt, April 1993. I. Occurrence of Prorocentrum Triestinum Schiffer (Red Tide) Bloom and Associated Physical and Chemical Conditions

A yellow-brown coloration of water developed in the Eastern Harbour of Alexandria (Egypt) during April 1993. the dinoflagellate Prorocentrum triestinum, the causative organism, culminated in a population peak of 71-10⁶ cells 1^-1, chlorophyll a nearly 361 μgl^-1. the bloom occurred with a thermohaline stratified water column and low surface nutrient levels. Water temperature was considered a crucial environmental factor controlling the occurrence of P. triestinum and nitrate was significantly correlated with its counts. the high relative growth constant (3.4 d^-1), calculated just prior to the massive occurrence of the species, explains the rapid development of the bloom. A comparison with the earlier phytoplankton studies in the harbour is made.     

Phytoplankton communities in aquaculture system (integration of shrimp and seaweed)

ABSTRACT

Knowledge about phytoplankton communities is important for aquaculture due to their influence on environmental variables. The goal of the study was to evaluate the ecological effect of seaweed Gracilaria birdiae at three different densities: 2.5 (LG2.5); 5.0 (LG5.0) and 7.5?kg m^?3 (LG7.5), on water quality variables and the phytoplankton communities in integrated aquaculture systems (shrimp and seaweed) with a control (without seaweed) (LB) using biofloc technology. Settleable and total suspended solids were significantly correlated with the phytoplankton groups. In addition, orthophosphate was the main variable controlling phytoplankton growth and gross primary production. No significant differences were identified among the treatments in terms of the phytoplankton assemblages (p?>?0.05) but differences were found between the communities (ANOSIM, R global?=?0.873) in relation to the days of the experiment. However, the LG2.5 treatment had higher diversity and lower species dominance, as well as higher productivity and final shrimp weight. The results indicate that seaweed inhibit phytoplankton growth, mainly of toxic species. They suggest that phytoplankton composition in integrated aquaculture systems in the presence of seaweed at a density of 2.5?kg m^?3 is more diversified and provides better water quality and shrimp performance by inhibiting the abundance of harmful species.     

Microplankton of the Gulf of Elat: Aspects of seasonal and bathymetric distribution

The components of 4 major groups of microplankton were identified and their numerical abundance determined in net samples collected at depth intervals down to 600 m at a permanent station off the H. Steinitz Marine Biological Laboratory, Elat. The samples analyzed were collected once a fortnight over a period of 1 year beginning in June 1974. The groups studied were the Cyanophyta, Bacillariophyta and Pyrrhophyta of the phytoplankton and the Tintinnina of the microzooplankton. The pattern of vertical distribution of the phytoplankton as a whole showed a general decrease in cell numbers with increasing depth. The blue-green algae, consisting mainly of Trichodesmium sp. trichomes, were confined primarily to the upper 100 m. The diatoms were unevenly distributed, with one species, a minute centric diatom, Thalassiosira subtilis, associated with a massive bloom during March 1975 between 300 and 400 m. The peridinians, the group with the largest number of species, included forms which were evenly distributed throughout the whole water column and forms limited either to the upper or deeper water strata in accordance with their light intensity preferences. The mass occurrence of newly-emerged dinoflagellate cysts of Pyrophacus horologicum, a weakly-armoured dinoflagellate, in the 200 to 300 m depth interval during April 1975, suggests that reproductive processes in dinoflagellates may also be light-controlled. The tintinnids, like the phytoplankton groups, were most abundant in the upper 100 m with a gradual decrease in numbers of individuals, though not in species, in the deeper water strata. The overall yearly pattern of microplankton distribution indicates 3 peaks: late fall and early summer peaks consisting primarily of blue-green algae and one in early spring consisting of several species of diatoms and peridinians and of species of tintinnids which thrive in the same niches as the phytoplankton. Both phytoplankton and tintinnid production was lowest during the summer months.     

Pathways of arsenic uptake and incorporation in estuarine phytoplankton and the filter-feeding invertebrates Eurytemora affinis,Balanus improvisus and Crassostrea virginica

Arsenic uptake from water and from phytoplankton was followed in the copepod Eurytemora affinis and the barnacle Balanus improvisus collected from the Patuxent River estuary, Chesapeake Bay, eastern coast of the USA in 1987, and in the oyster Crassostrea virginica obtained from a hatchery on the shore of Chesapeake Bay in 1987. Dissolved arsenic was readily taken up by phytoplankton and by shell material of B. improvisus and C. virginica; however, no dissolved arsenic was incorporated into the invertebrate tissues. When E. affinis, B. improvisus and C. virginica were fed phytoplankton containing elevated arsenic contents, significant arsenic incorporation occurred. Juvenile B. improvisus incorporated relatively more arsenic than adults of all three species. Compared to the 100 to 200% increase in arsenic content by phytoplankton exposed to dissolved arsenic, the 25 to 50% increase in these invertebrate species via trophic transfer is relatively small. Even though the trophic pathway for arsenic transfer is the major one for higher trophic levels within an ecosystem, the potential for direct arsenic impact to trophic levels other than phytoplankton appears to be minimal.     

Variation in cadmium uptake by estuarine phytoplankton and transfer to the copepod Eurytemora affinis

The pathways of cadmium (Cd) uptake and transfer within an estuarine planktonic community from the Patuxent River, Maryland, USA, were investigated using an assemblage of natural phytoplankton and the copepod Eurytemora affinis Poppe. The experiment was carried out in October 1992 in replicated 500-liter, flow-through, fiberglass tanks. Growth rate, species composition, and Cd loading affected the accumulation of Cd by the phytoplankton. Uptake of Cd by phytoplankton was proportional to the amount of Cd available in the water column. Partition coefficients (K _d) for phytoplankton uptake averaged 4.4 × 10⁴. As metal loading rates and phytoplankton species composition changed during the 12-d experiment, Cd partitioning declined. Transfer of Cd to E. affinis occurred from Cd-laden phytoplankton, with levels in the copepods being approximately the same as, or somewhat less, than in the phytoplankton. Some Cd uptake occurred in copepods exposed to dissolved Cd only; however, the uptake was considerably less than that seen from food. Thus, Cd content of higher trophic levels, such as copepods, can be affected by the degree of Cd incorporation in their food source, and by ecological factors regulating phytoplankton ingestion. Received: 13 September 1995 / Accepted: 29 October 1998     

Heavy Metal Concentrations in Sea Urchin Tissues From Egypt,Ireland and United Kingdom

Abstract

Sea urchins (Paracentrotus lividus) were collected from the Mediterranean coast off Alexandria, Egypt and the Atlantic coast of Ireland to the west of Galway. Samples of another urchin species, Psammechinus miliaris, were collected from the entrance to Southampton Water, U.K. Both the Alexandria coast and Southampton Water receive domestic and industrial waste water inputs whilst the western Irish coast is relatively unpolluted.

Sampled animals were dissected to separate coelomic fluids, Aristotle's lantern, gonads and tissue (digestive tract plus connective tissue). the concentrations of heavy metals (cadmium, copper, lead, nickel and zinc) in the different parts were measured using flame atomic absorption spectroscopy.

Many levels of heavy metals in the different parts were similar in specimens taken across the wide range of sites and the two species. A notable exception was the high level of copper (33 μg g^?1 dry wt.) and zinc 328 μg g^?1? dry wt.) in urchin tissue from Southampton Water.

The metal concentrations in the gonads of Paracentrotus lividus are of particular interest because of human consumption of this species. the highest levels of copper (3.3–5.2 g^?1? dry wt.) and zinc (74–181 μ g^?1? dry wt.) dry wt.) in gonads were found in the samples from Egypt. Data from this study are compared with other results reported from the Mediterranean.

A simple, short term, elevated water column copper uptake experiment was undertaken with Paracentrotus lividus which showed an increase in gonad concentrations of this element.     

Distribution of phytoplankton communities in relation to the large-scale hydrographical regime in the Fram Strait

In June and July 1984 phytoplankton distribution was investigated in the Fram Strait between Greenland and Svalbard. Chlorophylla, particulate organic carbon, nitrate and phytoplankton species composition were determined from six different depths in the upper 200 m of the water column. Multivariate analysis methods were applied to identify phytoplankton communities in relation to different hydrographic regimes. Three main domains could be distinguished in terms of both hydrography and biology: (1) the East Greenland shelf polynya with a high biomass mainly produced by chain-forming diatoms, (2) the ice-covered East Greenland Current with an extremely low standing stock dominated by flagellates and (3) the marginal ice zone with a biomass maximum in 20 to 40 m depth formed by diatoms, dinoflagellates andPhaeocystis pouchetii.     

宁波市某人工泻湖浮游生物变化特征及影响因素分析

以宁波市北仑区梅山水道形成的人工泻湖为研究对象,在不同季节进行水质及浮游生物调查,分析其浮游生物时空分布特征与水质的关系。4个采样点共检出浮游植物66种,以硅藻为绝对优势种,检出浮游动物25种,主要为桡足类、少量轮虫及网纹虫;拦坝后水道内浮游生物密度有了数量级增长,各项生物评价指数降低,但各采样点仍处于中污染水平。监测理化参数表明,研究水域在拦坝后盐度下降、悬浮物浓度下降,氮磷含量无明显变化;水域大部分点位处于中度富营养化水平。结合浮游生物分布与理化参数进行分析,发现堤坝合龙后,水道内侧海水淡化、悬浮物含量下降,导致浮游生物密度上升、生物多样性下降、出现淡水优势种群;营养盐含量不是浮游生物生长的限制因子,对浮游生物分布无显著影响。     

Seasonal changes in antibacterial activity of North Sea water

During 1969 and 1970, the antibacterial activity of North Sea water was investigated at Helgoland (southern North Sea). Tests were performed with resting cells of Escherichia coli, Staphylococous aureus and Serratia marinorubra, inoculated in freshly sampled sea water used raw or after filter sterilization. Simultaneously, growth of indigenous bacterial populations which occurred in the presence, as well as in the absence (only 1970), of test bacteria was controlled. Seasonal changes in inactivation of test cells and multiplication of marine bacteria were correlated with the life cycles of several diatom species. Breakdown of phytoplankton flowerings produced the most pronounced influence on antibacterial activity of sea water. Sometimes, enhancement of kill rate could be established during growth periods of various algal species, too. From the results obtained, it is concluded that the inactivation capacity of sea water depends, to a considerable degree, on the availability of nutritive organic matter, the concentration of which changes according to phytoplankton development. Strain-specific differences in resistance to inimical action of sea water are, in part, correlated with the ability of test cells to use, and to compete with, marine bacteria for nutrients from the sea. A somewhat modified interpretation of antibacterial activity of sea water is presented.     

Persistent diel rhythms in the chlorophyll fluorescence of marine phytoplankton species

The diel periodicities of in-vivo chlorophyll fluorescence and DCMU-enhanced chlorophyll fluorescence of 47 marine phytoplankton species were examined for 2 d in a 14 h L:10 h D light: dark cycle and then in continous light for another 2 to 3 d. Almost all phytoplankton species exhibit a more rapid increase in in-vivo fluorescence and DCMU-enhanced fluorescence during the light phase than during the dark phase. About one-half of the species examined exhibited persistent diel rhythms in continous light, indicating the operation of a biological clock. No phylogenetic or habitat related trends as to which species exhibited persistent rhythms were apparent. Of the phyla of eukaryotic phytoplankton adequately examined, none lacked biological clocks. Contrary to past hypotheses, some phytoplankton species maintain a persistent diel rhythm in a constant environment while reproducing at a rate greater than one division per day.     

First monospecific bloom of the harmful raphidophyte Chattonella antiqua (Hada) Ono in Alexandria waters related to water quality and copepod grazing

The massive red tide bloom of Chattonella antiqua that occurred in Alexandria waters during late August/early September 2006 was monospecific, of very high density, and of wide spatial distribution, and was accompanied by mass fish and invertebrates mortalities. During the bloom, surface water temperature ranged between 26.5 and 28.5 °C and salinity between 23 and 27 psu. The bloom started under very high nitrate and ammonia levels; where the uptake of ammonia seemed to be faster than that of nitrate, and the bloom seemed to avoid the copepod grazing. Mass fish and invertebrates mortality was observed. Few cells of Heterosigma species have been reported for the first time in the Alexandria waters. Several environmental constraints (including physical factors), nutrient loading, copepod grazing and comparison with other data for C. antiqua blooms in Alexandria waters are also discussed.     

Long-term changes in phytoplankton phenology and community structure in the Bahía Blanca Estuary, Argentina

The phytoplankton of the Bahía Blanca Estuary, Argentina, has been surveyed since 1978. Chlorophyll a, phytoplankton abundance, species composition and physico-chemical variables have been fortnightly recorded. From 1978 to 2002, a single winter–early spring diatom bloom has dominated the main pattern of phytoplankton interannual variability. Such pattern showed noticeable changes since 2006: the absence of the typical winter bloom and changes in phenology, together with the replacement of the dominant blooming species, i.e. Thalassiosira curviseriata, and the appearance of different blooming species, i.e. Cyclotella sp. and Thalassiosira minima. The new pattern showed relatively short-lived diatom blooms that spread throughout the year. In addition, shifts in the phytoplankton size structure toward small-sized diatoms, including the replacement of relatively large Thalassiosira spp. by small Cyclotella species and Chaetoceros species have been noticed. The changes in the phenology and composition of the phytoplankton are mainly attributed to warmer winters and the extremely dry weather conditions evidenced in recent years in the Bahía Blanca area. Changing climate has modified the hydrological features in the inner part of the estuary (i.e. higher temperatures and salinities) and potentially triggered the reorganization of the phytoplankton community. This long-term study provides evidence on species-specific and structural changes at the bottom of the pelagic food web likely related to the recent hydroclimatic conditions in a temperature estuary of the southwestern Atlantic.     

Continuous plankton records: Changes in the composition and abundance of the phytoplankton of the north-eastern Atlantic ocean and North Sea, 1958–1974

In most areas of the north-eastern Atlantic Ocean, diatoms have declined drastically in abundance in the last decade. Additionally, in areas to the north of 59°N Ceratium species and an index of total phytoplankton have also declined. South of 59°N the phytoplankton index has increased, diatoms have declined and Ceratium species have remained at a constant level of abundance. A possible explanation of the increase in the phytoplankton index at a time when the diatoms were declinig south of 59°N is the development of unidentified phytoplankton organisms such as microflagellates. As many of the variables influencing phytoplankton standing crop are governed in turn by the prevailing weather, the phytoplankton changes may well be a consequence of the general deterioration, since 1940, of North Atlantic weather. Changes in phytoplankton which may be attributed to an amelioration of climate since 1971 are evident as yet only in the southern North Sea.     

Temperature tolerance of embryos and larvae of five bivalve species under simulated power plant entrainment conditions: a synthesis

Upwelling effects of subsurface water on phytoplankton growth were evaluated by 9 simulated culture experiments of coastal upwelling. Particular attention was paid to the effects of nutrient enrichment on the surface phytoplankton by the upwelling of nutrient rich subsurface water and of the exposure of the subsurface phytoplankters to surface radiation. The following are the results obtained: the lag period of phytoplankton growth was inversely related to water temperature; the maximum yield of phytoplankton was proportional to the amounts of available initial nutrients; the specific growth rates of phytoplankton were a function of both the initial nutrient concentrations and water temperature; and the maximum specific growth rate was simply proportional to water temperature. According to the relations found, a simple equation is presented for the estimation of phytoplankton growth in a given upwelling. Succession of species in the phytoplankton assemblage in upwelled water mass was also taken into consideration.     

富营养化水体降磷对浮游植物群落结构特征的影响

浮游植物是水生态系统中物质循环和能量流动的基础,作为初级生产者,浮游植物的群落结构直接影响着水生态系统的结构和功能。在水产养殖生产中,如何根据养殖生物对生活环境的需求开展精准培水、定向培水,培养养殖生物所需要的浮游植物,在维持养殖水域生态平衡的同时又能为养殖生物提供一定的饵料资源,这一直是摆在水产科技工作者面前的重要难题和研究热点。已有的资料大都是通过添加磷的方式研究磷改变对浮游植物生长的影响,而有关富营养化水体降磷对浮游植物群落结构影响的研究尚未见报道。为此,试验通过向取自富营养化湖泊的水体中加入磷去除剂,采用Pielou均匀度指数、Mcnaughton优势度指数和Shannon多样性指数,研究自然水体中的磷被降低后水体浮游植物群落结构的变化情况。结果表明,所取富营养化水体中共检出绿藻（Chlorophyta）、硅藻（Bacillariophyta）、蓝藻（Cyanophyta）、裸藻（Euglenophyta）、隐藻（Cryptophyta）、甲藻（Pyrrophyta）6门29种（包括变种和变型）;其中绿藻、蓝藻、硅藻、隐藻、裸藻、甲藻分别有7、4、2、1、1种,分别占总种数的24.13%、13.79%、6.90%、3.45%、3.45%。富营养化水体降磷后,虽然试验组和对照组在浮游植物种类组成上没有差异,但浮游植物群落结构特征发生了很大变化,浮游植物数量明显降低,由13 238.8×104cells·L-1降低至3 997.5×104cells·L-1,下降了69.8%;浮游植物优势种从1门（蓝藻（Cyanophyta））6种增加到3门（绿藻（Chlorophyta）、硅藻（Bacillariophyta）、蓝藻（Cyanophyta））12种,优势度指数从97.29%降低至86.30%,优势种门数和优势种种数远远高于对照组,优势度明显低于对照组;同时,浮游植物多样性指数和均匀度分别从1.85和0.38升高至2.60和0.54,显示出试验组浮游植物多样性和均匀度优于对照组。研究表明富营养化水体降磷对浮游植物群落结构产生了明显影响,使群落结构处于更加复杂、完整和稳定的状态。     

Long-term change of the marine environment and plankton in the Xiamen Sea under the influence of climate change and human sewage

ABSTRACT

Long-term observations of the Xiamen Sea in Fujian Province were used to analyze variations in sea temperature, salinity, inorganic nitrogen (N), activated phosphate (P), and phytoplankton, as well as the features of red tides. Results showed that in recent decades, sea temperature and concentrations of N and P nutrients increased while salinity decreased attributed to climate warming, rainfall, and human sewage. In addition, reduction in the number of phytoplankton species and rising abundance of phytoplankton indicated that the structure of phytoplankton community presented a simplified and minimized trend which magnified the dominance of dominant phytoplankton species. Since 2000, red tides have occurred more frequently, and the eutrophic-type diatom species, Skeletonema costatum appears to be the predominant species. Data suggested that variations of N and P nutrients exert a potent and rapid influence on phytoplankton than sea temperature and ocean salinity.     

Coccolithophores: a major phytoplankton component in mature upwelled waters off the Cape Peninsula,South Africa in March, 1983

Coccolithophores, together with other phytoplankton, were sampled at ten stations along a transect following the general orientation of the Cape Peninsula upwelling plume in March, 1983. Thirteen coccolithophore species were identified with Emiliania huxleyi dominating the assemblages. Coccolithophores and other microflagellates were more abundant than diatoms along the transect except at one station in mature upwelled water. Very high populations (2 340×10³ cells l^-1) of coccolithophores were found in mature upwelled water adjacent to the oceanic front. This count is one of the highest counts ever recorded in an upwelling area. The anomalous warm event prior to sampling may have had a residual effect on seeding, contributing towards the predominance of small-celled phytoplankton over chain-forming diatoms.