Limitations of Population Growth

Table 2: Mann-Whitney U statistical testing for the difference in average heart rate of Daphnia before and after the addition of aged water:

Daphnia, also known as water fleas, are small crustaceans about 1mm-5mm long and are part of the freshwater zooplankton (Ebert 2005, Hutchinson 2005 & Clifford 1991). Daphnia can be found in most fresh water habitats such as freshwater springs, ponds and reservoirs and are the predominant food for planktivorous fish. Dapnia are ‘filter feeders’ meaning they feed on small particles suspended in the water which can include algae. It has been found that daphnia tend to migrate to the upper parts of the water at night and return to the lower parts of the water in the day to hide from predators (Ebert 2005) (Hutchinson 2005). Daphnia can reproduce through sexual reproduction and also asexual

In this research paper I will talk about how a large decrease in the algae population in the Chesapeake Bay will cause problems for not just fish and other species but the people who fish and make a living off of it. A large decrease in algae population will have a domino effect on the food chain. Having a major decrease in algae will hurt how others species live and protect themselves.

The additional species, Daphnia Pulex are a derivative from Daphnia Magna, which can be in located rain filled tire ruts and any stable body of water. These daphnia are established in fresh water and maintain the highest concentrations of daphnia compared to other species can be found in lakes and ponds. Daphnia magna is a water flea dependent on environmental conditions to breed and survive. Conditions such as temperature, salinity and oxygen levels can be detrimental to the lifespan of these organisms (Elenbaas, 2013. Within their existing environment daphnia consume algae, bacteria and detritus; it is this continual uptake of these organisms, which maintains the food chains integrity. Daphnia also host a number of bacteria, fungi, nematodes,

The population dynamics of Daphnia magna are observed under three different conditions; low, medium, and high density. The effects of different population densities on the survivorship and reproduction of Daphnia are observed over a two-week period within a lab environment. Over the two week period, the numbers of parent Daphnia alive and dead are recorded daily, along with the amount of offspring produced each day. From the main parameter investigated, the net reproductive rate, the results of the experiment support that higher densities result in less successful reproduction and decreased fecundity. Values for the instantaneous growth rate of the populations also suggests that low and medium density populations allow for

Hypothesis: High amounts of algae growing in the salt marsh will cause a large decrease in the mud snail population.

The purpose of this experiment is to understand the effects of nutrient enrichment and eutrophication, using samples of water from Rio Salado and Encanto Park. The samples will contain different concentration levels of nitrogen, phosphorous and nitrogen and phosphorous combined and the impact it has on algae growth. The results recorded showed that the nitrogen concentration levels had a little change, phosphorous levels had a higher change and phosphorous and nitrogen combined had a significantly higher change, resulting in higher algae growth. The results showed that phosphorous indeed is a limiting nutrient in algae growth, but to achieve the highest growth rate, both nitrogen and phosphorous need to be combined.

The effects of MP exposure on life history parameters were tested in a 21-d reproduction test according to OECD guidelines at one concentration of each particles size: 1000 particles/L (0.1,1,10 µm), subjected to the environment concentration about 1.1 items/mL has been reported(Moore et al., 2011). In brief, there were triplicates for each control and treatment group an experimental series. Five neonates (< 24h) were incubated respectively in 50 mL medium at 22 ℃ under a 12:12 light dark cycle of 1600 lux and fed 4.2×104 cell/mL a day of the micro alga Chlorella vulgaris. The test medium was fully replaced every day along with calculating the cells of C.vulgaris the daphnia ate everyday by blood cell

Daphnia are used to test water toxicity, they are a vital part of fresh water ecosystems. They are a food source for smaller fish and invertebrates and considered to be a consumer of algae and bacteria (Elbert, 2005). These small crustaceans range in size from 2-5mm long and are commonly referred to as water fleas. Daphnia belong to the group called Daphniidae, which is a relative of freshwater shrimp. It is easy to see the internal organs of daphnia because of a transparent taco shell like carapace. A carapace is the hard outer part of a shell or covering. A daphnia’s life span can range between 1-56 days. (Elenbaas, 2013; Clare 2002). The comfortable pH level for daphnia is between 7.2 and 8.5 (Clare, 2002).

Many elements influence population and its future growth, and thus affect life tables. These include, but are not limited to: birth, death, environment, habits, and socioeconomic status. It is necessary to monitor changes in these factors, especially birth rate and death rate,

Despite their proximity, the reef systems of Tela and Utila differed dramatically in D. antillarum population sizes, indicating that the population in Tela had recovered significantly post-mortality compared to Utila, where the population was still being supressed. D. antillarum in Utila also had a notably smaller average test size compared to Tela, likely due to a larger juvenile urchin population. Juveniles are less effective at grazing down algae populations and display significantly greater preference over the genera of algae they consume. In areas highly populated by juveniles, this would allow domination of certain fleshy brown genera such as Dictyota whilst species of the Caulerpa genus are grazed to a more regular coverage (Rivera and Turner, 2009). On Tela, individuals were more likely to reach maturity and grow larger; implying that on Utila there was a presence of ecological barriers limiting survival to maturity, which were not present on Tela. The rate of herbivory in each area highlights the importance of D. antillarum as a keystone species, as the Utilan reef showed clear signs of deterioration in health due to the dominance of fleshy-brown macroalgae (48.6%) and low coverage of scleractinian coral (19.4%) compared to Tela. The Tela reef showed a 68.3% dominance of scleractinian coral and significantly lower fleshy brow macro-algae coverage at 13.7%. This was particularly notable for a region with an average reported coral cover of <10% (Gardner et al., 2003).

Discussion The purpose of the paramecium study was to observe how two species, P. aurelia and P. caudatum, interacted with each other. Could the two species coexist? Or would one dominate the other. Twice daily for two weeks each ecology lab sections counted the paramecium stock.

The studies were printed in a special issue of Fisheries magazine this week, published by the American Fisheries Society. The scientists observed different changes in how inland fish reproduce, grow and where they can live.

Figure 4. Percentage increase in weight of Arenicola Marina over a period of 90 minutes when exposed to varying dilutions of seawater. Values are mean ± SEM. N=6 for 75%

These results suggest that the K. brevis counts are significantly increasing by more than quadrupling in number over a three day time frame, which is indicative of an impending harmful algal bloom. With this rate of increase, it is safe to speculate that a full algal bloom will occur in approximately 2.5 more days. There are other methods that may be used to investigate growth rates of bacteria, and these include filtration, measuring turbidity with a colorimeter or spectrophotometer, and using the most probable number method (Reikowski, 2013).