Browsing by Subject "Copepod"

Now showing 1 - 2 of 2

Effects of crude oil, chemical dispersant, and UV radiation on copepod nauplii from the Gulf of Mexico
(2015-05) Harvey, Tracy E.; Buskey, Edward Joseph, 1952-; Erdner, Deana; Liu, Zhanfei
Anthropogenic oil spills continue to have devastating effects on the ecosystems in which they occur. Understanding how marine ecosystems are affected by these events is important for future mitigation and the improvement of preventative and restoration methods. The goal of this study was to investigate how copepods, the predominant group of zooplankton and base of the marine food web, respond under oil spill conditions. Two important and novel aspects were included: (1) exposing copepods at an early life stage when individuals tend to be more vulnerable to contaminant exposure and (2) including UV radiation as a factor in toxicity analysis. Three species of copepod nauplii, native to the Gulf of Mexico, were exposed to concentrations of crude oil (0.5-2 µL/L) and chemical dispersant (0.5 µL/L) for 48 hours. Survival, growth, and swimming behavior of the copepod nauplii were examined. At relatively low concentrations of oil (≥1 µL/L) sublethal effects were observed, including changes in growth and swimming behavior. Most notably, oil (1 µL/L) + dispersant, in the presence of UV caused a significant increase in mortality by 8X and oil (2 µL/L) in the presence of UV caused a significant increase in mortality by 13X, compared to the controls. A LC50 of 2.0 µL/L of crude oil was observed without UV exposure and a LC50 of 1.3 µL/L of crude oil was observed in the presence of UV. These results demonstrate the importance of considering factors such as UV exposure, chemical dispersant, and life stage when evaluating the potential toxicity of an oil spill to marine organisms.
Evasion from predation : the perilous life of planktonic copepods throughout development
(2011-05) Gemmell, Bradford James; Buskey, Edward Joseph, 1952-; Strickler, J. Rudi; Holt, G. Joan; Lenz, Petra; Shank, G. Christopher
As one of the most abundant metazoan groups on the planet, copepods are found in virtually all marine environments. They provide a key link in marine food webs between photosynthetic algae and higher trophic levels. Subsequently, copepods are preyed upon by a wide variety of organisms throughout their life history. As a result copepods have evolved a powerful escape behavior at all stages of development, in response to hydrodynamic stimuli created by an approaching predator. Typically copepods exhibit 6 naupliar stages and 5 copepodite stages before becoming adults. This work focuses on quantifying the effectiveness of the escape behavior during key periods of development. The earliest developmental stage of copepod (nauplius N1) experiences the greatest amount of viscous forces and may be at a disadvantage when exposed to larger predators at cold temperatures. The results show that the nauplius exhibits a compensatory mechanism to maximize escape performance across its thermal range. Later in development, the nauplius (N6 stage) molts into a copepodite (C1 stage) which resembles the body form of an adult copepod. Here, there is a significant morphological change with little change in mass. Escape capabilities are investigated for key stages in response to feeding strikes from natural fish predators. The results demonstrate that the improvement in escape capability of the C1 stage is effective only against certain modes of predation. Finally, successfully escaping from predation has evolutionary fitness implications and adults (post C5) are the only reproductive stage. Some species have developed unique mechanisms to avoid predation such as breaking the water surface and making aerial escapes to avoid predators while in other cases, the predator has developed unique morphology in order to reduce the amount of hydrodynamic disturbance in the water which improves capture success of copepods. By investigating copepod behavior and their ability to avoid predation at various stages of development, we can begin to understand which stages copepods are most susceptible to different types of predators and how the escape response changes as development progresses. This can help in understanding localized abundances or deficiencies of both predator and prey in the marine food web.