Influence Of The Mississippi River On Pseudo-nitzschia spp. Abundance And Toxicity In Louisiana Coastal Waters

The presence of domoic acid (DA) toxin from multiple species of Pseudo-nitzschia is a concern in the highly productive food webs of the northern 1,* 2,3 2 1 1,4 1 1 2 3 4 Gulf of Mexico. We documented the Pseudo-­nitzschia presence, abundance, blooms, and toxicity over 3 years along a transect ∼100 km west of the Mississippi River Delta on the continental shelf. Pseudo-nitzschia were present throughout the year and occurred in high abundances (\u3e10 cells l ) in the early spring months during high Mississippi River (MSR) flow (∼20,000 m s ) but were most abundant (\u3e10 cells l ) when MSR discharge was relatively lower among the spring months. A high particulate toxin production (maximum reaching 13 μg DA l ) was associated with the high cell abundances and exceeded, by an order of magnitude, prior reports of particulate DA concentrations in Louisiana coastal waters. Differences in Pseudo-­nitzschia peak times and its toxicity were correlated mainly with the timing and magnitude of MSR discharge and changes in associated parameters such as nutrient stoichiometry and salinity. A negative relationship between high MSR discharge and Pseudo-­nitzschia and particulate DA concentrations was documented. These riverine dynamics have the potential to influence DA contamination in pelagic and benthic food webs in the coastal waters of the northern Gulf of Mexico

An alternative preperation method for studying diatom frustules using scanning electron microscopy (SEM)

Diyatomların tanımlanması ve sınıflandırılmasında, silis içeren hücre duvarı yapıları önemli bir taksonomik kriterdir. Bu makalede, organik materyalin valv yapısının incelenmesini zorlaştırması nedeni ile diyatom früstüllerinden oksidasyon yöntemi ile uzaklaştırılması için bilinenlere alternatif bir yöntem önerilmiştir. Bu yöntemle çalışılacak örneklerin, farklı ortamlardan (su, mide ve dışkı gibi) toplanılması halinde hangi modifikasyonların uygulanabileceği konusunda önerilerde bulunulmuştur.The structure of silica cell wall is an important taxonomic criterion in describing and classification of diatoms. In this study, because organic material in cells can block seeing the valve structures of diatom cell walls, an alternative preperation method was suggested using scanning electron microscopy to identify diatom fragments by cleaning diatom frustules from organic material using an oxidation method. Also some suggestions were given on which modifications can be applied when the source of the samples are collected from different medium such as water, gut contents and fecal samples

Can Crude Oil Toxicity on Phytoplankton Be Predicted Based on Toxicity Data on Benzo(a)Pyrene and Naphthalene?

Polycyclic aromatic hydrocarbons (PAHs), which are major components of crude oil, are responsible in large part for the toxicity of crude oil to phytoplankton. This study addressed the following question. Can reliable predictions of the aquatic toxicity of crude oil, a multi-component mixture, be described from toxicity data on individual PAH compounds? Naphthalene, the most abundant PAH compound, and benzo(a)pyrene, a highly toxic PAH compound, were selected as model compounds to quantify toxicity of crude oil on two phytoplankton species, Ditylum brightwellii and Heterocapsa triquetra, by analyzing the effects of different concentrations of these PAHs on growth rate. EC50 values suggested that the diatom D. brightwellii was more vulnerable to both toxicants than the dinoflagellate H. triquetra. However, a previous study, which investigated the impact of crude oil on the same two species, had opposite results. The differences in response from these phytoplankton species to naphthalene and benzo(a)pyrene toxicity compared to their response to crude oil suggest that they may not be solely used as surrogates to assess crude oil toxicity on phytoplankton

Responses of sympatric Karenia brevis, Prorocentrum minimum, and Heterosigma akashiwo to the exposure of crude oil

Impacts of the Deepwater Horizon oil spill on phytoplankton, particularly, the tolerability and changes to the toxin profiles of harmful toxic algal species remain unknown. The degree to which oil-affected sympatric Karenia brevis, Prorocentrum minimum, and Heterosigma akashiwo, all of which are ecologically important species in the Gulf of Mexico, was investigated. Comparison of their tolerability to that of non-toxic species showed that the toxin-production potential of harmful species does not provide a selective advantage. Investigated toxin profiles for K. brevis and P. minimum demonstrated an increase in toxin productivity at the lowest crude oil concentration (0.66 mg L-1) tested in this study. Higher crude oil concentrations led to significant growth inhibition and a decrease in toxin production. Findings from this study could assist in the assessment of shellfish bed closures due to high risk of increased toxin potential of these phytoplankton species, especially during times of stressed conditions

Distinct responses of Gulf of Mexico phytoplankton communities to crude oil and the dispersant corexit(A (R)) Ec9500A under different nutrient regimes

This study examines the potential effects of exposure to South Louisiana sweet crude oil (LSC), Corexit(A (R)) EC9500A, and dispersed oil on enclosed phytoplankton communities under different nutrient regimes. Three distinct microcosm experiments were conducted for 10 days to assess changes to the structure of natural communities from the Gulf of Mexico as quantified by temporal changes in the biomasses of different phytoplankton groups. Concentration of NO3, Si and PO4 were 0.83, 0.99 and 0.09 mu M for the unenriched treatments and 14.07, 13.01 and 0.94 mu M for the enriched treatments, respectively. Overall, the contaminants LSC and Corexit(A (R)) EC9500A led to a decrease in the number of sensitive species and an increase in more resistant species. Phytoplankton communities showed more sensitivity to LSC under nutrient-limited conditions. The addition of nutrients to initially nutrient-limited treatments lessened the inhibitory effect of LSC in the short term. Centric diatoms benefited most from this enrichment, but pennate diatoms demonstrated considerably greater tolerance to crude oil at low crude oil concentrations in nutrient-enriched treatments. Dinoflagellates showed relatively higher tolerance in nutrient-limited treatments and high crude oil concentrations. Corexit(A (R)) EC9500A inputs significantly increased the toxicity of crude oil. Corexit(A (R)) EC9500A alone had a highly inhibitory effect at 63 ppm on phytoplankton communities. This study highlights the fact that different nutrient regimes play a major role in determining the shifts of the phytoplankton community in response to exposure to different concentrations of crude oil and dispersant. Determination of the functional equivalence of shifted phytoplankton groups could complement our research and allow for more pertinent extrapolation to real world conditions

How Were Phytoplankton Affected by the Deepwater Horizon Oil Spill?

A literature review demonstrates that crude oil spills can affect phytoplankton, favoring the growth of some while inhibiting the growth of others. Subsequently, the phytoplankton assemblage can change as a result of exposure to crude oil. Studies of phytoplankton responses to the Macondo (Deepwater Horizon) oil spill indicate that the phytoplankton may have been stimulated by the oil spill, although the presence of low-salinity water in the region makes it difficult to discount the importance of riverine-borne nutrients as a factor. A few studies suggest that the oil spill was toxic to some phytoplankton species, whereas others indicate that the degree of tolerance to the oil or to dispersants differs among species. These results generally comply with findings of previous studies, but a lack of published field data analyses prevents further assessment of the impacts of the Deepwater Horizon oil spill on phytoplankton population dynamics in the northern Gulf of Mexico

Toxic Diatom Pseudo-nitzschia and Its Primary Consumers (Vectors)

Toxic algal blooms are occurring on a more frequent basis and have been shown to cause harm in higher trophic levels. The diatom toxin domoic acid, produced by the genus Pseudo-nitzschia, has been shown to be responsible for the contamination of shellfish, zooplankton, and fish around the world. Contaminations have impacted various economical markets as well. These primary consumers (vectors) have a variety of responses to blooms of toxic phytoplankton species ranging from avoidance to ingestion of the algae. To define their role in toxin transfer, it is necessary to know their position in the food web and their response to toxic food species. If the toxin is transferred via these vectors, it can cause a serious intoxication in humans, marine birds, and mammals

Türkiye kıyılarından potansiyel olarak toksik,yeni bir tür kaydı, Pseudo-nitzschia calliantha Lundholm, Moestrup& Hasle 2003

Türkiye kıyılarından potensiyel olarak toksik, yeni bir tür kaydı, Pseudo-nitzschia calliantha Lundholm, Moestrup & Hasle 2003. Diatomlardan Pseudo-nitzschia'nm bazı türlerinin dünyanın bir çok bölgesinde insanlar da dahil yüksek organizasyonlu organizmaların ölümlerinden sorumlu olduğu ve bir nörotoksik aminoasit olan domoik asit'i ürettiği bilinmektedir. Bu çalışmada, elektron mikroskobu kullanılarak, potansiyel olarak toksik olabilecek bir Pseudo-nitzschia türü olan P. calliantha, Türkiye'nin Karadeniz kıyılan için ilk kez rapor edilmiştir. P. calliantha'nın tanımlanması morfolojik incelemelere dayanarak yapılmıştır.Several species of the diatom Pseudo-nitzschia H. Peragallo in H. & M. Peragallo, 1897-1908 are known to produce domoic acid (DA), a neurotoxic amino acid that has been shown to be responsible for deaths of higher trophic-level organisms, including humans, in many areas around the world. In this study, one of the potentially toxic Pseudo-nitzschia species, P. calliantha, is documented for the first time from the Turkish Part of the Black Sea using transmission and scanning electron microscopy. P. calliantha is described based on morphological data