Compositional change of bacterial communities in oil-polluted seawater amid varying degrees of nanoplankton bacterivory.

Petroleum hydrocarbons are being released into the marine environment continuously. They will undergo weathering and may eventually be biodegraded by bacteria and other microbes. While nanoplankton (2-20 μm) are the major consumers of marine bacteria, their effect on the process of biodegradation of oil hydrocarbons is still debated.

Impaired grazing of marine protozoa in sub-lethal exposure to the water accommodated fraction of crude oil and dispersant.

Despite the advances in safety technology and the improved implementation of precautionary measures, crude oil pollution has been occurring in the oceans globally. The water accommodated fraction (WAF) of crude oil and chemical dispersant are hypothesized to cause sub-lethal adverse effects on marine protists that are pivotal consumers of primary production. Exposure experiments were conducted to investigate the effects of crude oil and dispersant pollutants on the growth and grazing, separately, of protozoa species in cultures.

Exposure methodologies for dissolved individual hydrocarbons, dissolved oil, water oil dispersions, water accommodated fraction and chemically enhanced water accommodated fraction of fresh and weathered oil.

Characterizing the nature and effects of oil released into the marine environment is very challenging. It is generally recognized that "environmentally relevant" conditions for exposure involve a range of temporal and spatial conditions, a range of exposure pathways (e.g.

De-coupled phytoplankton growth and microzooplankton grazing in a simulated oil spill event in mesocosms.

Microzooplankton (<200 μm) are essential intermediates between primary production and organisms at the higher trophic levels. Their ecological functions could be substantially affected by crude oil pollution. A natural plankton community was exposed to 10 μL L of chemically dispersed crude oil (DOil) in outdoor mesocosms for 7 days, with control (Ctrl) mesocosms set up for comparison.

Marine phytoplankton responses to oil and dispersant exposures: Knowledge gained since the Deepwater Horizon oil spill.

The Deepwater Horizon oil spill of 2010 brought the ecology and health of the Gulf of Mexico to the forefront of the public's and scientific community's attention. Not only did we need a better understanding of how this oil spill impacted the Gulf of Mexico ecosystem, but we also needed to apply this knowledge to help assess impacts from perturbations in the region and guide future response actions. Phytoplankton represent the base of the food web in oceanic systems.

Potential effects of bacterial communities on the formation of blooms of the harmful dinoflagellate Prorocentrum after the 2014 Texas City "Y" oil spill (USA).

The association between phytoplankton blooms and oil spills is still controversial despite numerous studies. Surprisingly, to date, there have been no studies on the effect of bacterial communities (BCs) exposed to crude oil on phytoplankton growth, even though crude oil changes BCs, which can then affect phytoplankton growth and species composition. Co-culture with crude oil-exposed BCs significantly stimulated the growth of Prorocentrum texanum in the laboratory.

Development of Swimming Abilities in Squid Paralarvae: Behavioral and Ecological Implications for Dispersal.

This study investigates the development of swimming abilities and its relationship with morphology, growth, and nourishment of reared paralarvae from hatching to 60 days of age. Paralarvae (2.5-11 mm mantle length - ML) were videotaped, and their behavior quantified throughout development using computerized motion analysis.

Oil Spills and Dispersants Can Cause the Initiation of Potentially Harmful Dinoflagellate Blooms ("Red Tides").

After oil spills and dispersant applications the formation of red tides or harmful algal blooms (HABs) has been observed, which can cause additional negative impacts in areas affected by oil spills. However, the link between oil spills and HABs is still unknown. Here, we present experimental evidence that demonstrates a connection between oil spills and HABs.

Rapid alterations to marine microbiota communities following an oil spill.

Field data from the first several days after an oil spill is rare but crucial for our understanding of a spill's impact on marine microbiota given their short generation times. Field data collected within days of the Texas City "Y" oil spill showed that exposure to crude oil can rapidly imbalance populations of marine microbiota, which leads to the proliferation of more resistant organisms. Vibrionales bacteria were up to 48 times higher than background concentrations at the most impacted sites and populations of the dinoflagellate Prorocentrum texanum increased significantly as well.

Wastewater influences nitrogen dynamics in a coastal catchment during a prolonged drought.

Ecosystem function measurements can enhance our understanding of nitrogen (N) delivery in coastal catchments across river and estuary ecosystems. Here, we contrast patterns of N cycling and export in two rivers, one heavily influenced by wastewater treatment plants (WWTP), in a coastal catchment of south Texas. We measured N export from both rivers to the estuary over 2 yr that encompass a severe drought, along with detailed mechanisms of N cycling in river, tidal river, and two estuary sites during prolonged drought.

Escapes in copepods: comparison between myelinate and amyelinate species.

Rapid conduction in myelinated nerves keeps distant parts of large organisms in timely communication. It is thus surprising to find myelination in some very small organisms. Calanoid copepods, while sharing similar body plans, are evenly divided between myelinate and amyelinate taxa.

Dynamic sinking behaviour in marine phytoplankton: rapid changes in buoyancy may aid in nutrient uptake.

Phytoplankton sinking is an important property that can determine community composition in the photic zone and material loss to the deep ocean. To date, studies of diatom suspension have relied on bulk measurements with assumptions that bulk rates adequately capture the essential characteristics of diatom sinking. However, recent work has illustrated that individual diatom sinking rates vary considerably from the mean bulk rate.

Can gelatinous zooplankton influence the fate of crude oil in marine environments?

Gelatinous zooplankton are known for their capacity to excrete copious amounts of mucus that can be utilized by other organisms. The release of mucus is exacerbated by stressful conditions. Despite the recognized importance of cnidarian mucus to production and material flux in marine ecosystems, the role of gelatinous zooplankton in influencing the fate of oil spills is unknown.

Influence of UVB radiation on the lethal and sublethal toxicity of dispersed crude oil to planktonic copepod nauplii.

Toxic effects of petroleum to marine zooplankton have been generally investigated using dissolved petroleum hydrocarbons and in the absence of sunlight. In this study, we determined the influence of natural ultraviolet B (UVB) radiation on the lethal and sublethal toxicity of dispersed crude oil to naupliar stages of the planktonic copepods Acartia tonsa, Temora turbinata and Pseudodiaptomus pelagicus. Low concentrations of dispersed crude oil (1 μL L(-1)) caused a significant reduction in survival, growth and swimming activity of copepod nauplii after 48 h of exposure.

How much crude oil can zooplankton ingest? Estimating the quantity of dispersed crude oil defecated by planktonic copepods.

We investigated and quantified defecation rates of crude oil by 3 species of marine planktonic copepods (Temora turbinata, Acartia tonsa, and Parvocalanus crassirostris) and a natural copepod assemblage after exposure to mechanically or chemically dispersed crude oil. Between 88 and 100% of the analyzed fecal pellets from three species of copepods and a natural copepod assemblage exposed for 48 h to physically or chemically dispersed light crude oil contained crude oil droplets. Crude oil droplets inside fecal pellets were smaller (median diameter: 2.

Simultaneous measurement of 3D zooplankton trajectories and surrounding fluid velocity field in complex flows.

We describe an automated, volumetric particle image velocimetry (PIV) and tracking method that measures time-resolved, 3D zooplankton trajectories and surrounding volumetric fluid velocity fields simultaneously and non-intrusively. The method is demonstrated for groups of copepods flowing past a wall-mounted cylinder. We show that copepods execute escape responses when subjected to a strain rate threshold upstream of a cylinder, but the same threshold range elicits no escape responses in the turbulent wake downstream.

A tale of the ciliate tail: investigation into the adaptive significance of this sub-cellular structure.

Ciliates can form an important link between the microbial loop and higher trophic levels primarily through consumption by copepods. This high predation pressure has resulted in a number of ciliate species developing rapid escape swimming behaviour. Several species of these escaping ciliates also possess a long contractile tail for which the functionality remains unresolved.

Novel insight into the role of heterotrophic dinoflagellates in the fate of crude oil in the sea.

Although planktonic protozoans are likely to interact with dispersed crude oil after a spill, protozoan-mediated processes affecting crude oil pollution in the sea are still not well known. Here, we present the first evidence of ingestion and defecation of physically or chemically dispersed crude oil droplets (1-86 μm in diameter) by heterotrophic dinoflagellates, major components of marine planktonic food webs. At a crude oil concentration commonly found after an oil spill (1 μL L(-1)), the heterotrophic dinoflagellates Noctiluca scintillans and Gyrodinium spirale grew and ingested ~0.

Massive outbreaks of Noctiluca scintillans blooms in the Arabian Sea due to spread of hypoxia.

In the last decade, the northern Arabian Sea has witnessed a radical shift in the composition of winter phytoplankton blooms, which previously comprised mainly of diatoms, the unicellular, siliceous photosynthetic organisms favoured by nutrient-enriched waters from convective mixing. These trophically important diatom blooms have been replaced by widespread blooms of a large, green dinoflagellate, Noctiluca scintillans, which combines carbon fixation from its chlorophyll-containing endosymbiont with ingestion of prey. Here, we report that these massive outbreaks of N.

Dispersant Corexit 9500A and chemically dispersed crude oil decreases the growth rates of meroplanktonic barnacle nauplii (Amphibalanus improvisus) and tornaria larvae (Schizocardium sp.).

Our knowledge of the lethal and sublethal effects of dispersants and dispersed crude oil on meroplanktonic larvae is limited despite the importance of planktonic larval stages in the life cycle of benthic invertebrates. We determined the effects of Light Louisiana Sweet crude oil, dispersant Corexit 9500A, and dispersant-treated crude oil on the survival and growth rates of nauplii of the barnacle Amphibalanus improvisus and tornaria larvae of the enteropneust Schizocardium sp. Growth rates of barnacle nauplii and tornaria larvae were significantly reduced after exposure to chemically dispersed crude oil and dispersant Corexit 9500A at concentrations commonly found in the water column after dispersant application in crude oil spills.

Toxicity of dispersant Corexit 9500A and crude oil to marine microzooplankton.

In 2010, nearly 7 million liters of chemical dispersants, mainly Corexit 9500A, were released in the Gulf of Mexico to treat the Deepwater Horizon oil spill. However, little is still known about the effects of Corexit 9500A and dispersed crude oil on microzooplankton despite the important roles of these planktonic organisms in marine ecosystems. We conducted laboratory experiments to determine the acute toxicity of Corexit 9500A, and physically and chemically dispersed Louisiana light sweet crude oil to marine microzooplankton (oligotrich ciliates, tintinnids and heterotrophic dinoflagellates).

Ingestion and sublethal effects of physically and chemically dispersed crude oil on marine planktonic copepods.

Planktonic copepods play a key function in marine ecosystems, however, little is known about the effects of dispersants and chemically dispersed crude oil on these important planktonic organisms. We examined the potential for the copepods Acartia tonsa, Temora turbinata and Parvocalanus crassirostris to ingest crude oil droplets and determined the acute toxicity of the dispersant Corexit(®) 9500A, and physically and chemically dispersed crude oil to these copepods. We detected ingestion of crude oil droplets by adults and nauplii of the three copepod species.

Morphology of seahorse head hydrodynamically aids in capture of evasive prey.

Syngnathid fish (seahorses, pipefish and sea dragons) are slow swimmers yet capture evasive prey (copepods) using a technique known as the 'pivot' feeding, which involves rapid movement to overcome prey escape capabilities. However, this feeding mode functions only at short range and requires approaching very closely to hydrodynamically sensitive prey without triggering an escape. Here we investigate the role of head morphology on prey capture using holographic and particle image velocimetry (PIV).

Effects of crude oil exposure on bioaccumulation of polycyclic aromatic hydrocarbons and survival of adult and larval stages of gelatinous zooplankton.

Gelatinous zooplankton play an important role in marine food webs both as major consumers of metazooplankton and as prey of apex predators (e.g., tuna, sunfish, sea turtles).