Authors:
Leslie Brinson, Alisa Benjamin, Myra Halpin, Mark Lyke, Suzanne McClung, Noel Nelson

Consultant:
Philippe Hensel

Introduction

Laguna Palo Verde in Palo Verde National Park, Guanacaste, Costa Rica, is currently a marsh. Twenty years ago while this area was a large cattle ranch it was a lagoon with open water and was used as a resting and feeding area for migratory birds. Palo Verde National Park was founded in part to preserve the lagoon. The cattle were removed from the area this did not have the expected result of restoring the area for bird habitat. Instead, the lagoon was invaded by Typha.(Geraldo Barbosa, personal communication). Now there is no open water. The marsh is now filled with sediment and vegetation including large areas of Typha spp (cattail) and Nymphaea spp (water lilies). Typha tends to grow densely even during the dry season. It chokes out other species and habitat for waterfowl. Nymphaea grow in wetlands that are filling with sediment and die out when the marsh is dry. (Hernandez and Gomez, 1993)

One of the reasons for the decline of migratory birds in the lagoon is the loss of habitat due to Typha. We decided to assess several aspects of the biodiversity of this area. First, we chose to compare the abundance and species richness of micro-invertebrates and protists found on the leaves of Nymphaea spp in Typha-dominated and non-Typha inhabitated areas. A study comparing two marsh areas, one with Typha and one without, done in August of 1993, showed no difference between the biodiversity of the two areas. We wondered whether this had changed over the last six years. (Donnelly et al, 1993) Secondly, we wanted to compare the biomass of Nymphaea spp in Typha-dominated vs. Typha-free areas.

The samples of water lilies were taken in two categories: plants found in open areas of the marsh and plants that were growing among the typha. Five sites in each category were chosen randomly and assayed. Each area was selected by placing the square meter frame over a patch of lilies. The depth within each square meter was measured in three random areas with a stick marked in increments of ten centimeters. The first step of sampling was to choose five plants with stems (within the plot) and place them in a liter of water in a plastic bag to later observe the microfauna living on the underside of the lilies. The second step was to harvest all the Nymphae located within the one meter frame. All leaves were counted and a random sample from each plot’s leaves was measured by length and width. Both areas were sampled using the same protocol. In the second area the Typha was cut with a machete or knife in order to access the lilies.

The microfauna samples were prepared by rinsing each bagged plot sample with tap water in a collection bowl and filtered to concentrate the microfauna. Forty-four milliliters of this fluid was removed from the liquid to observe in a petri dish under the microscope. A grid system using thin thread was used to separate the petri dish into four clockwise quadrants. Only the microfauna found along the gridlines and quadrant bisect were recorded for data. This procedure was repeated on four samples twice for the open area and two samples once from the area with Typha.

Results:

Summary of the measurement of leaves collected from ten plots.
 

No Thypha	length	width	l x w		water depth	leaf count
plot 1	15	12.9	196.4		50 cm	189
plot 2	17.3	14.3	267.45		60 cm	106
plot 3	16.6	13.4	234.4		67 cm	74
plot 4	11.2	9.16	111.8		48 cm	74
plot 5	8.2	7.2	63		54 cm	54
Total	68.3	56.96	873.05			497	total
Average	13.66	11.392	174.61			99.4	average
Thypha
plot 1	13.4	10.8	145.9		43 cm	4
plot 2	5.7	4.7	31.5		21 cm	127
plot 3	8	6.7	54		21.5 cm	96
plot 4	5.7	4.5	27.7		20 cm	112
Total	32.8	26.7	259.1		21 cm	0
Average	8.2	6.675	64.775			339	total
						67.8	average

1. There will be more diversity of microorganism on the leaves of nympha(sp) in the open areas compared to the area populated by typha/nympha. REJECTED
2. There will be more micro invertebrates and protists found on the leaves of nympha(sp) in the open area compared to the area populated by typha/nympha. REJECTED
3. There will be a greater biomass of nympha in the open water than in the typha/nympa area. SUPPORT

Data Table 1:

Nympha – No Typha
2 species of aphids					combined aphids species
	Total	%				Total	%
Golden Aphid	29	0.285	-0.15537
Gray aphid	58.8	0.578	-0.13761		aphids	87.8	0.864173	-0.05479
Cladoceran	0.75	0.0007	-0.00221		Cladoceran	0.75	0.007382	-0.01574
Ostracod	1	0.001	-0.003		Ostracod	1	0.009843	-0.01975
Euglena	0.25	0.0002	-0.00074		Euglena	0.25	0.002461	-0.00642
Ciliate	0.78	0.0008	-0.00248		Ciliate	0.78	0.007677	-0.01624
Paramecia	4.25	0.04	-0.05592		Paramecia	4.25	0.041831	-0.05766
Red Eyed Nymph	0.75	0.0007	-0.00221		Red Eyed Nymph	0.75	0.007382	-0.01574
Dragonfly	1	0.001	-0.003		Dragonfly	1	0.009843	-0.01975
Nymph case	3.8	0.037	-0.05298		Nymph case	3.8	0.037402	-0.05338
blue greens	0	0			blue greens	0	0
Volvox	0.25	0.0002	-0.00074		Volvox	0.25	0.002461	-0.00642
Snails	0.5	0.0005	-0.00165		snails	0.5	0.004921	-0.01136
Mites	0.5	0.0005	-0.00165		mites	0.5	0.004921	-0.01136
Shannon-Weiner Diversity Index			0.419544		Shannon-Weiner Diversity Index			0.288598
Nympha with Typha
	Total	%				Total	%
Golden Aphid	19.5	0.433	-0.1574
Gray aphid	12.5	0.278	-0.15456		Aphid	32	0.711111	-0.10529
Cladoceran	3	0.067	-0.07865		Cladoceran	3	0.066667	-0.07841
Ostracod	0.5	0.011	-0.02154		Ostracod	0.5	0.011111	-0.02171
Euglena					Euglena
Ciliate	2	0.044	-0.05969		Ciliate	2	0.044444	-0.0601
Rotifer	0.5	0.01	-0.02		Rotifer	0.5	0.011111	-0.02171
Spider	0.5	0.011	-0.02154		Spider	0.5	0.011111	-0.02171
Dragonfly	1.5	0.033	-0.04889		Dragonfly	1.5	0.033333	-0.04924
Nymph case					Nymph case
blue greens	2	0.044	-0.05969		blue greens	2	0.044444	-0.0601
Volvox					Volvox
Snails	2.5	0.056	-0.0701		snails	2.5	0.055556	-0.06974
Mosquito larvae	0.5	0.01	-0.02		Mosquito larvae	0.5	0.011111	-0.02171
Shannon-Weiner Diversity Index			0.712065		Shannon-Weiner Diversity Index			0.509719

The data reject the hypothes that there will be greater diversity in the open water nympha.

Hypothesis 2:

Data Table 2

Summary of Analysis of Organism Abundance on Nymphaea Species
	Open Water		Typha
	Sample 1	Sample 2	Sample 1	Sample 2
Total Organisms	78	125	70	20
Organism/Leaf	15.6	25.0	14.0	4.0
Mean Area per Leaf (cm2)	196.4	267.5	54.0	31.5
Mean Organisms/cm2	0.0794	0.0935	0.2593	0.1270
Mean Organisms/cm2 for plot type	0.0865		0.1931
Standard Deviation	0.0099		0.0935
t-test calculation	1.276
t-test table value	3.182

At the 95% confidence level there is no difference in abundance of micro-organism per leaf area. The data rejects the hypothesis that there will be a higher abundance of micro-organisms in the open water nympha.

Hypothesis 3:

Data Graph 1

 

Discussion:

In studying Laguna Palo Verde, we had expected to see greater species diversity of micro invertebrates on water lily leaves in the non-Typha areas. Shannon-Weiner index analysis of our data indicated that the opposite was true Unfortunately, this analysis was not really appropriate for our data. The leaves of the water lilies in the Typha areas were mostly smaller than those found in the non-Typha areas. The Shannon-Weiner analysis did not take the surface area of the leaves into account. Also, the total number of organisms on the leaves from the Typha areas was too small for the Shannon-Weiner analysis to be valid.

In order to correct for the difference in leaf surface area, the abundance of micro invertebrates per square centimeter of leaf was determined. A t-test at the 95% confidence level indicated no significant difference between the abundance of micro invertebrates in the Typha areas and non-Typha areas. This is similar to the findings of Donnelly et al. (1993).

Leaf length and surface area measurements were much larger in the non-Typha areas. This supported our hypothesis that the biomass of water lilies would be greater in non-Typha areas. It is important to note, however, that the depth of water in the Typha areas was significantly lower than in the non-Typha areas. The lower water depth may also contribute to the smaller size of leaves in the Typha areas. It is not possible to conclude from our data whether the presence of the Typha is the cause of smaller leaf size in our data.

Literature Cited:

Barbosa, Geraldo. 1999. Personal communication, Palo Verde National Park.

Donnelly, Maureen et al. August, 1993. "Comparison of aquatic macroinvertebrate populations from two marsh microhabitats in Palo Verde National Park." OTS Tropical Studies.

Hernandes Esquivel, Daniel and Gomez Laurito, Jorge. 1993. Flora Aquatica del Humedal de Palo Verde. Editorial de la Universidad Nacional de Costa Rica.
 

"Essential Question"

Inquiry Based Applications of Our Research Project at Palo Verde
Our group members generated the following ideas for application.

Applications:

1. Diversity Studies- this type of research project will help illustrate biodiversity
2. Competition between species
3. Habitat specialization
4. Population studies
5. One meter sampling
6. Could be used with any aquatic location (i.e. healthy vs. sick)

1. Sampling techniques
2. Counting techniques
3. Microscope skills
4. Identification invertebrate water species

1. Remediated /restored ecosystems
2. Succession of ecosystem
3. Multi or four year historical data file for ecosystem
4. Seasonal ecosystem studies
5. Food chains/ food webs
6. Outreach programs…..State Fish & Wildlife, U.S. Fish & Wildlife

1. Math computation methods
2. Observation skills
3. Written language
4. History of area
5. Spanish/science content based
6. Social Issues