productivity as the result of excessive anthropogenic impacts. With Galveston Bay we have to 
opportunity to act—to identify and reduce or eliminate these impacts—before it is too late. 
The initial symptoms of stress have already appeared. The brown pelicans and other species have 
disappeared, oyster populations are greatly reduced, seagrasses are almost nonexistent, wetlands 
are being nibbled away around the entire bay periphery, sediment import has been drastically 
reduced, and freshwater inflow is threatened. Heretofore, each individual action has been judged 
independently, as if other development impacts do not exist. Clearly, consideration of the Galveston 
Bay ecosystem demands a holistic approach. 
Many environmental perturbations can produce cumulative effects (10). When materials, espe¬ 
cially toxicants, are added to the environment from multiple sources water quality can deteriorate, 
leading to changes in the species composition of the biota and alteration of the links in the food web. 
A second major type of cumulative effect can result from the repeated removal of materials or 
organisms from the environment. Intense fishery harvests, especially when combined with natural 
environmental changes, can lead to population collapse if a critical, usually unknown, threshold is 
passed. A third kind of cumulative effect can result from environmental changes over large areas and 
long periods, as, for example, extensive dredging operations and open-water spoil disposal that 
affect bottom habitat. More complicated cumulative effects arise when stresses of different types 
combine to produce a single effect or suite of effects. If channel enlargement was to resuspend 
toxicants and increase saltwater intrusion at the same time that freshwater inflow was reduced, 
salinity increases might permit invasion of oyster predators, parasites and pathogens and result in 
further inroads to an already depressed oyster population. Complex cumulative effects also occur 
when many individual areas in a region are repeatedly altered, as with periodic maintenance 
dredging and open-water spoil disposal. Large contiguous habitats can be fragmented into ever- 
smaller patches separated by inhospitable areas, making it difficult for organisms to locate and 
maintain populations in disjunct habitat fragments. 
Cumulative impacts may also occur when perturbations are crowded in time, so close together 
that the effects of one perturbation are not dissipated before the next occurs. Cumulative impacts also 
result from disruptions so close in space that their effects overlap. Different types of disturbances 
occurring in the same area can interact synergistically to produce qualitatively different responses 
by the receiving ecological communities. Indirect effects can be produced after a perturbation has 
ceased, or produced some distance away from the site of initial disruption, or result from a complex 
intervening pathway. Incremental and decremental effects can include time and space crowding, as 
well as removal of habitat piece by piece, and result in a "nibbling" away of environmental quality 
and quantity. Threshold developments that stimulate additional activity in a region or projects 
whose environmental effects are delayed (time lags) or are felt over large distances (space lags) can 
produce cumulative effects if their impacts overlap in time or space or are synergistic with those of 
other developments. Examples of not just some, but all of these actions are planned or proposed for 
Galveston Bay and its watershed. 
Information Need 
A comprehensive assessment of the cumulative impacts of all of the present, planned and 
proposed projects that could affect Galveston Bay is critically needed. The assessment should be 
conducted by an independent third party and its design and planning must involve all of the federal 
and state agencies responsible for natural resource protection. 
Ecosystem Interconnections 
Just as phenomena occurring in the riverine and upland ecosystems feeding and surrounding 
Galveston Bay will affect its community structure and productivity, the bay, in turn, exerts significant 
effects on the Gulf of Mexico. The interactions between rivers and the bay, and between bay and gulf 
through the tenuous Bolivar Roads connection, require further study. 
Information Needs 
Many ecosystem-wide and inter-ecosystem questions need to be addressed. How will modifica¬ 
tion of freshwater inflow or saltwater intrusion affect bay circulation, temperature structure, 
productivity, fisheries, ecological communities, and critical habitats? The biota of the lower Trinity 
river habitats is dominated by marine organisms; will construction of a dam near the mouth of the 
river have significant impacts on marine productivity? Will an increase in wastewater discharges to 
the San Jacinto River drainage be functionally equivalent to the concomitant decrease in freshwater 
inflow from the Trinity River? How will bay and continental shelf circulation be affected by 
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