On the other hand, it is clear from Table 7 that the Western 13 area has a
much shorter residence time. This area receives 70 of the total freshwater discharge to the lagoon and discharges estuarine mixed waters to the adjacent
Gulf through El Carmen Inlet, often with a velocity 80 cm sec
-1
. The calculated residence time for this area is about one month. This reflects the net eastward
flow through the lagoon, the strongly tidal Carmen inlet, and the high fresh water input.
5. Management implications
5.1 Identifying Indicators and a monitoring protocol Indicators for measuring the effects of changes in freshwater, both in quantity
and quality, on biological and ecological characteristics and functioning of the lagoon, should reflect the factors that affect these changes. These include
climate change, normal environmental variability i.e., normal year to year variation in rainfall, and human activities i.e., urban development, agricultural
activities in the coastal plain freshwater wetlands, oil and gas activities, over- fishing, dredging and filling in freshwater wetlands and mangrove swamps,
deforestation in the watershed, and freshwater diversions.
We suggest eleven parameters as potential indicators for a robust monitoring
program to document the impacts of changes in freshwater input: 1 soil and water salinity, 2 turbidity and water transparency, 3 soil accretion and
elevation change, 4 mean chlorophyll-a, 5 nutrient concentrations, 6 oxygen concentration, 7 coliform bacteria, 8 change in seagrass biomass and
distribution
,
9 mangrove litterfall, 10 mangrove stem growth, and 11 river
discharge. If all of these parameters cannot be measured, a subset can be chosen.
38
Figure 22 shows the location of suggested sampling sites appropriate for a
monitoring program. The locations of these sites are based on the functional
dynamics of Terminos Lagoon and the habitats or subsystems defined in Table 2
and Figure 10. These sampling sites cover the two Inlets, the Inner littoral of
Carmen Island, the Central Basin, and the Fluvial-lagoon system inlets to the lagoon.
Site 1 = Puerto Real Inlet Site 2 = Inner Littoral Carmen Island Isla Pajaros
Site 3 = Estero Pargo Inlet Site 4 = Carmen Inlet
Site 5 = Central Basin western Site 6 = Central Basin mid western
Site 7 = Central Basin mid eastern Site 8 = Central basin eastern
Site 9 = Fluvial-lagoon Candelaria river inlet Site 10 = Fluvial-lagoon Chumpan river inlet
Site 11 = Fluvial-lagoon Palizada river inlet Site 12 = Fluvial-lagoon Atasta inlet
For monitoring the water column Sites 1 to 12, we recommend consideration of the following parameters and frequencies of sampling:
1. Continuous measurement of water level with tide gauges at one location in
