La Selva Biological Station,Costa Rica

Water & Soil: "Going Bananas"

Denise Gordon

"Drowned rats"

Introduction

Banana production is an extremely important product providing jobs and money for Costa Rica. The first commercial banana plantation was started in 1872 in the Zent Valley, the southern area of Costa Rica. The market has fluctuated throughout the early 1900’s due to disease, but new strains of bananas were introduced to again strengthen and promote banana plantation. Unregulated production has allowed banana plantations to use and dispose of insecticides, herbicides and fertilizers as they see fit. The environmental impact because of man’s intervention to the local environment will be investigated through the chemical and biotic analysis around a local banana plantation and a protected primary forest.

Question

Do man’s activities (e.g., growing bananas) negatively affect the biodiversity of organisms?

Hypothesis

Higher values were expected in copper, nitrate and phosphate readings downstream from a banana plantation than in a La Selva primary forest stream. Lower pH readings and lower diversity of macroinvertebrates were expected downstream from the banana plantation than in a La Selva primary forest stream.

Methods

Four sites were selected -- two downstream from the Standard Fruit Company’s Finca Zurci #2 Banana Plantation in Puerto Viejo and two within the primary forests of La Selva Biological Station. The first two sites (Banana1 and Banana2) were visited one morning (17 July 2001, about 75 minutes apart), and the latter two sites [Sendero Sura (SUR950) and Camino Circular Cercano (CCC1050)] were visited the next morning (18 July 2001, about 60 minutes apart). Each site included three sampling locations that were five meters apart.

At each sampling location,

All biological observations and chemical testing occurred in the laboratory. Each stream sample was tested for copper, nitrates, phosphates, and pH. Each soil sample was tested for nitrates, phosphates, and pH. Each sample was also visually inspected for the presence of macroinvertebrates.

The data were collected, recorded, organized and analyzed.

Significance

We were interested in determining if we could quantify human impact and global environmental change by evaluating biological and chemical parameters of water quality in a relatively undisturbed site and one that we knew to be altered by commercial agriculture activity. Testing was not performed on the property of Standard Fruit Company’s Finca Zurci #2 Banana Plantation as permission was denied.

Observations:

(to see data and charts, click on the appropriate button in left-hand window.)

Banana Plantation

Weather: partly sunny to sunny

Sampling Date & Time: Tuesday, 17 July 2001

        0800 – 0910 & 0914 – 1004

Stream:

First Site (entirely upstream from road bridge): muddy bank, chocolate brown plume

Second Site (spanned road bridge): rocky bank

Soil: strong foul odor, dark blue-gray color

La Selva

Weather: cloudy & raining

Sampling Date & Time: Wednesday, 18 July 2001 0800 – 0845 & 1000 – 1050

Stream: less turbid, more colorless

First Site (spanned trail bridge): muddy bank

Second Site (spanned trail bridge): muddy bank

Soil: wetter, good smell

Copper: Higher copper concentrations were seen in two sites downstream from the banana plantation than two streams in La Selva Biological Station.

Nitrates: Higher nitrate concentrations were seen in two sites downstream from the banana plantation than two streams in La Selva Biological Station.

pH: In general, higher pH values were observed in two sites downstream from the banana plantation than two streams in La Selva Biological Station.

Phosphates: Higher phosphate concentrations were seen in two sites downstream from the banana plantation than two streams in La Selva Biological Station.

Biodiversity: There was equal biodiversity in the water of the two sites downstream from the banana plantation and in the water of two streams in La Selva Biological Station. There was also more biodiversity found in the soil samples La Selva Biological Station than downstream from the banana plantation.

Discussion

Once again, the hypothesis was:

"Higher values were expected in copper, nitrate and phosphate readings downstream from a banana plantation than in a La Selva primary forest stream. Lower pH readings and lower diversity of macroinvertebrates were expected downstream from the banana plantation than in a La Selva primary forest stream."

We were interested in determining if we could quantify human impact and global environmental change by evaluating biological and chemical parameters of water quality in a relatively undisturbed site and one that we knew to be altered by commercial agriculture activity. Before beginning testing, it was realized that there was one significant limitation in methodology. Due to time constraints, sampling occurred only once on two separate days. Because of this, categorical generalizations were not possible.

Copper: High values (> 1.0 ppm) probably indicate water that has been treated with copper to control algae or has been contaminated from untreated industrial wastes. As expected, higher copper concentrations were seen in two sites downstream from the banana plantation than two streams in La Selva.

Nitrates: Nitrogen is essential for plant growth. Excess amounts originate from agricultural fertilizers, sewage, industrial wastes, drainage from livestock feeding areas, and farm manures. As expected, higher nitrate concentrations were seen in two sites downstream from the banana plantation than two streams in La Selva.

pH: Most natural waters have a pH between 5.0 and 8.5. Lower pH values may indicate mine drainage or acid industrial wastes. Higher pH values may indicate alkaline industrial wastes. In general, higher pH values were observed in two sites downstream from the banana plantation than two streams in La Selva. This was an unexpected result.

Phosphates: Phosphorus is an important nutrient for aquatic plants. The amount found in water is generally low (< 0.1 ppm) unless the water is polluted from waste water sources or excessive drainage from agricultural areas. As expected, higher phosphate concentrations were seen in two sites downstream from the banana plantation than two streams in La Selva.

Biodiversity: Overall, there were fewer organisms found at all sites than was anticipated. There was equal biodiversity in the water of the two sites downstream from the banana plantation and in the water of two streams in La Selva. The organisms found at the banana plantation site were of the type that indicate poor water quality. And while there were more organisms found in the soil samples in two streams in La Selva than in the soil samples downstream from the banana plantation, there were far too few to reach any conclusions. It was noticed that the organisms were found at lower depths. Conditions (e.g., rain) were not favorable for observations. Most of the organisms were found on leaf litter, which was negatively affected by recent flooding.

Finally, it should be noted that the environmental temperature and the age of the water test chemicals are both factors that can degrade the effectiveness and sensitivity of the chemical tests.

Conclusions

Based upon our results, it does seem that at least the Standard Fruit Company’s Finca Zurci #2 Banana Plantation in Puerto Viejo, Costa Rica has altered the water quality of the streams that pass through its property. Biological and chemical tests both support the idea that the water quality is lower in the two streams tested downstream from the Standard Fruit Company’s Finca Zurci #2 Banana Plantation than the two streams tested at the La Selva Biological Station. Further testing in other streams in both of these areas would be necessary. However, concern about the water flowing through the Standard Fruit Company’s Finca Zurci #2 Banana Plantation does seem to be warranted at this time.