Neutral pH May Increase Species Richness

IntroductionAccording to Macintosh, countless variables could impact biodiversity, including temperature, pH, and salinity. With increasing human activity, these variables will change, potentially resulting in extinction of many species that cannot adapt fast enough. We analyzed mangroves and seagrasses to identify what conditions could impact biodiversity and better understand environmental preservation.

Hypothesis: Ho: In Biscayne Bay, the seagrasses will not have higher biodiversity than the mangroves.Ha: In Biscayne Bay, the seagrasses will have higher biodiversity than the mangroves.

Methods1. Prepare the sample kit

a. Plan to visit each site once this week and once next week. Use 3 sample cups during each collection.

b. Label pipets and straws. To avoid cross-contamination, do not use the same ones to collect samples from different habitats.

c. Label each of your 12 sample cups appropriately with Locality, Date, Transect #, and GPS coordinates

2. Go to Key Biscayne as the first collection site. 3. Lay the transect cord along the coast, and pull it straight 4. Back up 10m from the line5. From the 10m mark, at five different 20cm marks along

your transect, collect ~6mL water6. Place all five 6mL samples from one transect into the

same sample cup for a total of 30mL. This is the first sample.

7. Label the cup and its lid with locality, transect #, date, and time.

8. Collect three samples at this location.9. Repeat steps 3 to 8 at Biscayne Bay, the second

collection area.10. Test pH, temperature, and salinity.11. Use a dropper to remove water from the sample

container.12. Drop water onto a slide and look at it under a

microscope.13. Count how many of each species are present, as well as

the total number of organisms of each species.14. Next week, repeat all the steps

ResultsMangroves had a significantly higher species richness. We used the Mann-Whitney U test to quantify species richness. We first used Menhinick's index to assign each sample a diversity (D) value and rank them. The mangroves' average D value was 1.77. The seagrasses' average D value was 1.43. Based on our sample size of 6 for each habitat, according to the U-statistic test, a U value of 5 or less indicates 5% or less of overlap. After performing the U-statistic test on our data, we got a U value of 4. Therefore, our the difference in species richness in our two habitats is significant.

Besides counting species, we sampled pH, temperature, and salinity of both habitats. The temperature of the mangroves was 29*C while the temperature of the seagrasses was 28.5*C. Mangroves had a pH of 7.2 while seagrasses had a pH of 8.0. Both habitats had a salinity level of 30 ppt.

AcknowledgementsWe thank Professor Portales, Professor Dana Krempels, and Linda White.

Literature citedMacintosh, D.J., Ashton, E.C., 2002. A review of mangrove biodiversity conservation and management. Final Report 10/06/2002. Centre for Tropical Ecosystems Research, University of Aarhus, Denmark.

Hogarth, P., The Biology of Mangroves and Seagrasses Biology of Habitats Series. Oxford University Press (2007)

DiscussionOur results indicated the mangroves' species richness was significantly higher than the seagrasses'. Since both habitats had the same salinity, it is unlikely the difference is due to salinity. The similar temperatures of each environment makes it unlikely that temperature was the cause of the difference. However, the mangroves' pH is 7.2, close to neutral water, while the seagrasses' pH of 8.0 is more alkaline. According to Hogarth, alkaline water can have an increase of ammonia, which is a toxic nitrogenous waste.

This study suggests a pH closer to neutral helps increase biodiversity.

Andrea Zheng, Nicholas Lobato, and Alexander Burnett

A mangrove forest Seagrass

Downtown Miami, near Biscayne Bay