# Presentation: 042680

## ECOLOGICAL IMPACTSIDENTIFY AND CHARACTERIZE

## STRESSOR:

**FLOW ALTERATION**
_**HAZARD:**_
** **
**Increases in water velocity could result in scouring of bottom sediments in** **rivers and streams.  Conversely, decreases in water velocity could increase sedimentation rates.  Either would likely alter the benthic community.**
_**CHARACTERIZE**_** / **_**QUANTIFY:**_
**Can be important in small streams or rivers with flow-through facilities.  Ecological impacts would likely be minor on a national basis.  **

## STRESSOR:

**NUTRIENTS**
_**HAZARD:**_
**Nitrogen and phosphorus can stimulate aquatic plant growth, including nuisance species such a blue green algae.  In fresh water systems the limiting nutrient is phosphorus while nitrogen is limiting in marine systems.  Estuarine systems generally fall in between.**
**Eutrophic conditions (over fertilization) from aquaculture facilities can result from the deposition of feces and waste food.  Such conditions can have major ecological impacts.  Hypoxic or anoxic conditions in the water column can result due to BOD and COD from decaying algae.  Likewise, the benthic community can be impacted.  Shading by dense algal blooms can limit the photic zone thus affecting rooted aquatic plants.**

## Slide 4

## CHARCTERIZE / QUANTIFY:

_**CHARCTERIZE**_** / **_**QUANTIFY:**_
**There are mathematical models that can estimate dissolved oxygen concentrations resulting from anthropogenic nutrients.  Likewise, there is a vast literature on the dissolved oxygen requirements of aquatic organisms.  There are federal and dissolved oxygen standards.**
**Unfortunately, there is not a single model that will work everywhere and the models have to be calibrated for a particular water body.**

## STRESSOR:

**SOLIDS ( Suspended and Settleable = TSS)**
_**HAZARD:**_
**Turbidity due to suspended solids, primarily from uneaten food and feces, can decrease the photic zone and hence effect the growth of vascular plants and algae.  TSS can cause hypoxic or anoxic conditions in the water column since they have a high organic content.  They can also increase water temperature as the particles absorb the sun’s energy.  The benthic community can be altered as the particles settle.**
** **

## CHARACTERIZE / QUANTIFY

**TSS loads to the aquatic environment from aquaculture facilities can be quite high.  For instance, the median TSS loading for 12 flow-through trout hatcheries was 100,000 lbs/yr with a maximum of near 400,000 lbs/yr.  Mathematical models are available to estimate the ecological effects of TSS with the same caveats as for nutrients.**

## STRESSOR:

**PATHOGENS**
_**HAZARD:**_
**Pathogens may infect consumers of aquaculture products.  This is particularly true for molluscan shellfish operations, e.g. hepatitis from consuming oysters.  But since this rule excludes such facilities, the hazard to humans from aquaculture associated pathogens in likely small.**
_**CHARACTERIZE **_**/ **_**QUANTIFY:**_
** ****Not likely significant.**

## STRESSOR:

**TRACE METALS (Zn, Cu, Mn, Fe)**
_**HAZARD:**_
**Trace metals are often added to feed to insure that the essential dietary nutrients are provided.  Hence feces and uneaten feed are routes to the receiving waters.  Additional sources include disinfectants and machinery.  Copper compounds are used extensively as antifoulants in net/pen operations.  Copper is extremely toxic to aquatic organisms, especially in its free ion form.  Copper sulfate is often used to control algae.  Algal and vascular plant communities can be impacted leadinc to decreased photosynthesis.**

## CHARACTERIZE / QUANTIFY:

**There is a vast literature on the toxicity of dissolved trace metals to aquatic organisms.  Cu and Zn readily sorb to sediments which decreases their biological availability to water column organisms.  The impact of copper contaminated sediments depends on the characteristics and composition of the sediments in question.  Factors such as organic content and grain size are important.**