Endangered and Threatened Fishes in the Klamath River Basin Causes of Decline and Strategies for Recovery (2004) / Chapter Skim
Currently Skimming:
3. Current Status of Aquatic Ecosystems: Lakes
3. Current Status of Aquatic Ecosystems: Lakes
Pages 95-143
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 95... ...
The last in the sequence of main-stem clams, Iron Gate Dam, provides reregulation capability for the main stem of the I(lamath River as explainecT below. Of the lakes usecT for storage ancT routing, Upper I(lamath Lake, Clear Lake, ancT Gerber Reservoir support the largest populations of listecT suckers (see Chapter 6 for a cletailecT treatment of the suckers)
|
From page 97... ...
Reflecting the relative amounts of research or monitoring ancI the apparent ranking of lakes with respect to their importance for the enciangerecI ancI threatened fishes, this chapter clevotes most of its attention to Upper Klamath Lake, some to the other lakes that are used for storage anti routing of water, ancI some to waters above Iron Gate Dam that hoicI non-reproclucing populations of listecI suckers anti have the potential to affect coho downstream; the remnants of Tule Lake anti Lower Klamath Lake provide little lacustrine habitat at present, but offer potential for restoration. UPPER KLAMATH LAKE Description Upper Klamath Lake is the largest body of water in the Klamath basin anti is one of the largest lakes in the western United States (about 140 mid.
|
From page 98... ...
/ ~ i:. \ \ \~ A Link River Dam \ FIGURE 3-1 Bathymetric map of Upper Klamath Lake and Agency Lake showing depths at the mean summer lake elevation of 4,141 ft above sea level.
|
From page 99... ...
, but has required a revised approach to predicting water availabilities in any given year (Chapter 11. The USBR 10-yr plan is basecI on a commitment of USBR not to allow Upper I(lamath Lake to fall in any given year below the minimum water levels that were observed in 1990-1999 for four hycirologic categories of years ancI not to allow the interannual mean water levels for these categories to fall below recent interannual means (1990-19991.
|
From page 101... ...
Operations for the four hycirologic categories differ most notably in their lower extremes, which occur after luly. In comparison with a baseline condition, which USER defines as lacking I(lamath Project operations but with all project facilities in place, proposed operations typically produce water levels that are above the baseline between March anti the encI of lune anti below the baseline cluring the last half of the summer or fall (USER 2002a)
|
From page 102... ...
The remaining marshes are most strongly connected to the lake at high water anti are progressively less connected at lower water levels clown to about 4,139 ft above sea level, at which point they become clisconnectecI. Poor water quality in Upper Klamath Lake causes mass mortality of listecI suckers anti may suppress the suckers' growth, reproductive success, anti resistance to disease or parasitism.
|
From page 103... ...
This is the situation in Upper Klamath Lake. For the phytoplankton as a whole in Upper Klamath Lake, nitrogen is limiting (see below)
|
From page 104... ...
Early observations indicate that the waters were green, ancI thus eutrophic, at a time when water quality wouicI have been changed little from the natural state. If, as suggestecI by BoycI et al.
|
From page 105... ...
, interstitial phosphorus can be transferred to the water column simply by agitation.
|
From page 106... ...
Release of phosphorus from sediments also can occur without any movement of the sediments. If there is a substantial concentration gradient of soluble phosphorus between the sediment pore waters anti the overlying water, the potential exists for diffusion of phosphorus from the pore waters to the overlying lake water anti distribution of the releasecI phosphorus by ecicly diffusion or bulk mixing of the water column.
|
From page 107... ...
Loss of ferric iron facilitates exchange between the sediment pore waters anti the overlying water ancI releases phosphorus bouncI by ferric iron. The result can be release of large amounts of phosphorus from the sediments (internal loacling)
|
From page 108... ...
Ganf anti Oliver 19821. Nitrogen in Upper Klamath Lake The total nitrogen loacI to Upper I(lamath Lake has been calculated for total-maximum-ciaily-loacI (TMDL)
|
From page 109... ...
It is unknown, however, whether limnohumic acids or other substances clerivecI from wetiancis wouicI have been present in sufficiently high quantities to inhibit the growth of bluegreen algae uncler the original conditions of the lake or why this inhibition wouicI have been operating selectively on Aphanizomenon, given that other algae were abundant. Another possibility, apparently not proposed for Upper I(lamath Lake (although listecI by Geiger 20011' has to clo with light climate as influencecI by limnohumic acids.
|
From page 110... ...
Although it seems fairly certain that Aphanizomenon has come into dominance in Upper I(lamath Lake through human influences, the causal mechanisms of this unclesirable change in phytoplankton dominance remain unclear. Seasonal Development of Algal Biomass Regular sampling of phytoplankton biomass at multiple stations in 1990-1998 has proviclecI a substantial amount of information on the time course anti interannual variability of biomass clevelopment of Aphanizomenon in Upper I(lamath Lake (I(ann 1998, Welch anti Burke 20011.
|
From page 111... ...
(1996) proposed that water temperature wouicI show the most clirect control on the rate of increase in early spring, when other conditions for growth are favorable, ancI thus might be a goocI predictor of the elapsecI time between the beginning of the growing season ancI any particular biomass threshoicI that might be consiclerecI an algal bloom.
|
From page 112... ...
As a water column gets creeper, the mean light availability for incliviclual cells circulating in the water column cleclines because cells spencI a higher proportion of time at greater depth, where light is less available. The mocleling lecI Welch ancI Burke to conclucle that maximum algal biomass of Aphanizomenon in Upper I(lamath Lake wouicI be quite sensitive to mean clepth of the lake (Welch ancI Burke 2001' p.
|
From page 113... ...
4142 4143 300 200 150 00 50 ·92 ·94 O 4138 4139 ·97 ·91 ·90 ·96 ·98 ·93 ·95 4140 4141 4142 4143 Water Level (feet) FIGURE 3-6 Relationship of mean chlorophyll (above)
|
From page 114... ...
Thus, high pH is proposed as a direct cause of the phosphorus enrichment of Upper I(lamath Lake through internal loading during the growing season. As explained above, however, the importance of other mechanisms of internal loading cannot be ruled out, especially because internal loading substantially increases phosphorus concentrations before the lake reaches its peaks of algal abundance that are the cause of peaks in pH.
|
From page 115... ...
Welch ancI Burke (2001) argued on the basis of mocleling that higher water levels wouicI produce lower extremes of pH, which wouicI potentially benefit the suckers.
|
From page 116... ...
19991. Uncler oxic conditions, ammonia either is removed from the water column by autotrophs (which use it nutritionally)
|
From page 117... ...
A discontinuous polymictic lake shows alternation of the two very different conditions associated with mixed ancI stratified water columns. While the water column is unstratified, the lake shows minimal vertical differentiation in oxygen or other water-quality variables.
|
From page 118... ...
Furthermore, algal populations show substantial and prolonged decline. The prolonged decrease in oxygen appears to be the main cause of mass mortality of the endangered suckers during transition from a stratified to a fully mixed water column accompanied by the most
|
From page 119... ...
In the meantime, substantial harm can occur to enciangerecI suckers because oxygen concentrations remain low. An important practical question is whether the episodes of low clissolvecI oxygen throughout the water column are relatecI to water level.
|
From page 120... ...
Other factors being equal, creeper water columns are more stable, as acknowlecigecI by Welch anti Burke (20011; that is, one might expect higher water levels to produce greater mortality than lower water levels. However, given the complicating influence of numerous factors, inclucling weather, associations between clepth anti extremes of oxygen concentrations may be too variable to detect.
|
From page 121... ...
CURRENT STATUS OF AQ UATIC ECOSYSTEMS: LAKES Low Wind Speed 1 Water Column Stratifies loons of Oxygen in Lower Water Column 1 High Wind Speed 1 Water Column Mixes loom Dissolved Oxygen Throughout Lake Mass Mortality of Fish 121 Algal Mortality Reduced Photosynthetic Capacity, Higher Oxygen Demand FIGURE 3-9 Probable cause of low dissolved oxygen throughout the water column of Upper I(lamath Lake during the growing season leading to mass mortality of fish.
|
From page 122... ...
Measurements of oxygen concentrations uncler ice cover wouicI shecI aciclitional light on this issue. Overview of Water Quality in Upper Klamath Lake Poor water quality causes the mass mortality of the two enciangerecI sucker species of Upper Klamath Lake anti may also cause other, more subtle kincis of harm.
|
From page 123... ...
The hypothesis proposes that the basic cause of change in water quality of the lake is reduction in the supply of limnohumic acids to the lake, with a consequent increase in transparency or possibly even a decrease in inhibitory effects (toxicity of the acids to
|
From page 124... ...
Unlike the diatoms that prececlecI it, Aphanizomenon was able to offset the low nitrogen:phosphorus ratio of the lake by nitrogen fixation, thus allowing
|
From page 125... ...
A second factor is episodic stratification of the water column, which leacis to oxygen deficits in the bottom portion of the water column anti appears to cause algal mortality. Mixing causecI by wincly weather brings oxygen-poor water to the surface, along with ammonia.
|
From page 126... ...
As shown by the preceding review of available evidence, there is no scientific support for the proposition that higher water levels correspond to better water quality in Upper Klamath Lake. For example, mean and maximum abundances of algae, which are the driving force behind poor water quality, show no indication of a relationship with water level.
|
From page 127... ...
This is a highly speculative proposition, however. Because soluble phosphorus is available in quantity even at the encI of the growing season, it appears that internal loacling is sufficient to supersaturate the neecis of algae for phosphorus.
|
From page 128... ...
An engineering stucly of the possibility is already available (Home 20021. Because of the size of Upper I(lamath Lake ancI the speecI with which it can become anoxic toward the bottom of the water column cluring episodes of stratification, it is unlikely that oxygenation could be used in preventing low concentrations of clissolvecI oxygen from developing in the lower water column cluring stagnation or in restoring oxygen when the water column mixes at clepressecI oxygen concentrations.
|
From page 129... ...
It cliffers from Upper Klamath Lake in its consiclerably longer hyciraulic residence time ancI its very low output of water relative to input. One other important feature, which has to clo with water management, is the high interannual ancI interseasonal variation in storage volume of Clear Lake, which corresponcis to great variations in area ancI mean clepth (USER 19941.
|
From page 130... ...
Interannual variations in the welfare of the populations have been scrutinized, however, because of questions relatecI to the maximum permissible cirawclown of the reservoir in a ciry year or in a succession of ciry years. Monitoring of water quality ancI condition of fish in 1991-1995 proviclecI a goocI opportunity to evaluate extreme cirawclown because the water level in 1992 cleclinecI to its lowest point since the drought of the 1930s.
|
From page 131... ...
Aquatic macrophytic vegetation like that founcI in Upper I(lamath Lake is virtually absent from Clear Lake because of its wicle range of water levels. The water column of Clear Lake typically has a turbid appearance suggestive of fine inorganic particulate material that is continually suspenclecI by wincI-generatecI currents (USER 19941.
|
From page 132... ...
Although mortality was not observed, there were several indicators of stress, inclucling higher rates of parasitism ancI poor body condition. These indicators clisappearecI quickly as water levels climbecI in 1993 at the encI of the drought (USER 19941.
|
From page 133... ...
For reasons primarily having to clo with water quality, the low water levels of 1992 serve as a guideline for setting thresholds to protect the fish from stress. LOWER KLAMATH LAKE Lower Klamath Lake has been reclucecI to a marshy remnant by clewatering.
|
From page 134... ...
In the recent past, Sump 1B has been much less likely to hold aclult suckers than Sump 1A; it is shallower ancI has shown a higher rate of sedimentation than Sump 1A. It also appears to have worse water quality than Sump 1A.
|
From page 135... ...
The reservoirs cliffer physically in several ways that are likely to influence water quality. I(eno Reservoir ancI t.C.
|
From page 136... ...
Thus, coicI hypolimnetic water of the two deepest reservoirs tencis to be much more static hyciraulically than the upper water column cluring the stratification season, as wouicI be the case in a natural lake of similar depth; the main withcirawal occurs by way of the epilimnion. A small withcirawal (about 50 cfs)
|
From page 137... ...
Periodic episodes of severe oxygen clepletion may occur in the upper two reservoirs. One such event appears to have occurred in 2001, when the entire water column of I(eno Reservoir became hypoxic or anoxic (Figure 3-151.
|
From page 138... ...
Boyle, July 10 15 20 25 ~ T DO, mg/L Copco, July 0 5 10 15 Temperature,°C ~ ~ ' f DO, mg/L ~ Temperature,°C > Iron Gate, July 0 5 10 15 20 ' f Temperature,°C 20 25 25 30 3 ' DO, ma: FIGURE 3-14 Water temperature and dissolved oxygen (DO) in all main-stem reservoirs, July 2000.
|
From page 139... ...
Upper I(lamath Lake shows extremes of pH extending above 10, but such extremes are not characteristic of the reservoirs. For example, monitoring of Copco, Iron Gate, ancT t.C.
|
From page 140... ...
Observations from the fielcI suggest that substantial blooms of Aphanizomenon occur in both Copco ancI Iron Gate reservoirs (USFWS 20021. This wouicI not be surprising, given the strong seecling of these reservoirs with Aphanizomenon from Upper I(lamath Lake ancI the presence of large amounts of nutrients.
|
From page 141... ...
Mass mortality of large fish is caused by episodes of low clissolvecI oxygen throughout the water column. Very high pH anti high concentrations of ammonia, although more transitory than the episodes of low clissolvecI oxygen, may be important agents of stress that affect the health anti body condition of the fish.
|
From page 142... ...
Control of water quality in Upper I(lamath Lake by management of water level, within the range of lake levels observed cluring the l990s, has no scientific basis at present.
|
From page 143... ...
Better water quality, in combination with other favorable factors given in more cletail in Chapters 5 anti 6, appear to explain steady recruitment, diverse age structure, anti goocI body condition of these populations. Deterioration of body condition of the listecI suckers at a time of extreme cirawclown provide a rationale for the lower allowable threshoicis of water level in these lakes.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.