The Palo Verde lagoon is on the floodplain of the Tempisque River. It is bounded by the river on the south and by limestone hills on the other sides. "The lowland areas between the hills and the wetland are composed mainly of montmorillonite clay with 2 x 2 lattice structure of the clay micelles which permits considerable incorporation of water molecules during the wet season and a substantial dry season loss of water." (Jansen, p. 131) During cattle ranching times, an opening was made between the lagoon and the river which allowed continual exchange of water between the river and the wetland, especially during the wet season. The river drains numerous rice fields along its route and as a result carries much sediment and agricultural chemicals. When the park was set up, the opening between the river and the lagoon was closed. At present, the main sources of water entering the lagoon are rainfall and runoff from the higher areas, primarily forested areas on the limestone cliffs. However, there is still flooding on a regular basis (usually at high tides) about 12-18 times per year. All areas of the lagoon seemed to have consistent water levels of about 0.5 to 0.7 meters within 10 meters of the edge.

Two areas in the lagoon were surveyed. One is being invaded by Typha dominguensis (cattails) which is becoming the dominant plant in that area. The other area, while not open water, is covered by primarily low growing species, also invasive – primarily Eeichhornia crassipes (water hyacinth), Nymphaea ampla (a water lily with small, rounded leaves) and another water lily having larger leaves with toothed margins. There are mangrove areas along the river bank and an area of Parkinsoniia aculeata (palo verde tree) in a parallel band between the mangroves and the lagoon.

The Quebrada Mula site, in addition to rainfall, run off from surrounding areas, and much less frequent river flooding, could also be fed by surface water (quebrada means small stream) although this is not documented. It is bisected by a concrete bridge and a filled in road area, with a narrow, 4.5 meter opening between them. Under and on both sides of the bridge, as well as one other small area, there was open water, probably indicating deeper water (>2 meters). The water level in the marsh varied between very shallow (15-20 cm) to water probably over our heads. This wetland had numerous areas with significantly different characteristic vegetation. Some areas were covered in primarily low growing floating vegetation while others had tall grasses and arrowroot.

The park management has concerns that the invasive species found in the wetland areas are decreasing the biodiversity which could eventually limit the ability of the wetland to maintain a healthy ecosystem.
 
 

Sagittaria guyanensis 17 Water plaintain

Aeschynomone sensitiva 9 Pinnately compound leaf, small yellow flowers, floating white rope like, tuberous main root surrounded by mats of hair roots.

Nymphaea ampla 8 Small leafed, smooth edged white flowered water lily Grass A 50-60 Segmented grass with alternating leaves, reddish stem, 30 cm. above water, long underwater stems

Pistia stratiotes about 200 Small duckweed

Floating plant A 2 Water lettuce

Eleocharis mutata or 5 Sedge (triangular stalk), no seeds or Cyperus articulatus flowers. (found mostly along shore in C. digitatus 15-20 cm water)

Palo Verde – Low vegetation

Eichhornia crassipes 14 Water Hyacinth

Nymphaea ampla 24-30 Small leafed, smooth edged water lily stems and bottom of leaf reddish colored Water lily A 12-25 Larger, toothed edged lily with typical white Paspalum sp. < 5% Grass (Phillipe identified)

Potomogeton sp. <5% Fern like aquatic plant (seaweed)

Aeschynomone sensitiva 9 Pinnately compound leaf, small yellow flowers, floating white rope like, tuberous main root surrounded by mats of hair roots.

Minute yellow flower on 5-6 cm stalk with no leaves, rooted in floating roots of other plants
 

Quebrada Mula (4 separate 1 meter square lots)

We found Canna lutea (canna lily) in the wetland, but not in the area surveyed.

Eichhornia crassipes 100 Water Hyacinth

Grass A 50 Segmented grass with alternating leaves, Reddish stem, 30 cm. above water, long underwater stems
? 570 Fuzzy leafed (similar to Venus Flytrap), clumped with root ball, floating plants

Pistia stratiotes <1% Small duckweed

? 60 Floating seaweek (milfoil) type plant

Grass C 16 Sharp leafed, light green segmented grass

Grass D 23 Sharp leafed, dark green, segmented grass

Grass E 37 Hairy leafed and stem, medium green segmented grass
Mimosa pigra? 2 Herbaceous, thorned mimosa type legume

? 6 Water lettuce
? 10 Fuzzy deeply lobed palmate leafed, tall (1 m.) single stemmed, herbaceous plant
Vine with trifoliate leaf

Plants supposedly found in the lagoon (Crow), but unidentified by us are: Ludwigia inclinata, Najas guadalupensis, Nymphaea prolifera, Heteranthera limosa, Bacopa repens, , Neptunia plena, Paspalidium germinatum
 

Palo Verde Lagoon – Typha area - 7.6 kg.

Low vegetation 2.7 kg

Quebrada Mula 6.0 kg.
 
 

Palo Verde Typha

Core Sample #1

Mollusk #1 4 Small Snail Shells Planaspiral- light brown

Mollusk #2 6 Small fragments - white

Core Sample #2

Mollusk #1 4 Small Snail Shells Planaspiral -light brown

Mollusk #2 8 fragments -white

Core Sample #3

Mollusk #1 1 Large Snail Shell Planaspiral, White

Mollusk #2 1 Large Snail Shell Planaspiral Brown

Mollusk #3 6 Small Snail Shells 1 brown, 5 white

Mollusk #4 9 Small White Fragments

Mollusk #5 5 Small Brown Fragments

Core Sample #4

Mollusk #1 1 Large Snail , Planaspiral, Light Brown

Mollusk #2 3 Tiny White Shells Planaspiral

Mollusk #3 12 Shell Fragments -White helispiral

Mollusk #4 3 Shell Fragments Brown helispiral

Mollusk #5 Small white Bivalve
 
 

Palo Verde Low Vegetation- Core Sample #1

Mollusk #1 Large Half Snail, planaspiral light brown

Mollusk #2 3 Small Snail 1 helispiral white

2 planasprial light brown

Mollusk #3 Fragments 8 light brown

13 white

brown bivalve

Core Sample #2

Mollusk #1 2 Large Snail Shells both hosting aquatic plant growth

white helispiral

brown striped helispiral

Mollusk #2 2 Small Snail Shells planaspiral 19.0 mm. brown

8.3 mm. White

Mollusk #3 Fragments 3 helispiral brown

27 planaspiral white

Core Sample #3

Mollusk #1 1 Large Snail

Mollusk #2 1 Tiny Snail

Core Sample #4

Mollusk #1 1 Large Snail

Mollusk #2 3 Small Snail

Quebrada Mula

Core Sample #1

No living or dead mollusks were found

Core Sample #2

Mollusk #1 Large large snail Helispiral grey and white - Live

Mollusk #2 Large Snail Shell helispiral brown

Mollusk #3 2 Small Snail Shells helispiral brown

Core Sample #3

No living or dead organisms

Core Sample #4

Mollusk #1 2 Large Snails Striped dark brown and white helispiral - Live

Palo Verge Lagoon – Typha Very Rare Rare Occasional

Low vegetation None Very Rare Rare

Quebrada Mula Occasional Frequent Frequent

(Insect, protist)

Palo Verge Lagoon – Typha 7.5 7.5 8.0

Low vegetation 7/0 7.5 8.5

Quebrada Mula 5.5 5.5 5.5