Coldwater fish oxythermal habitat in Minnesota lakes: influence of total phosphorus, July air temperature, and relative depth

Abstract

An empirical model was developed that describes the influence of lake productivity, climate, and morphometry on coldwater fish oxythermal habitat. An oxythermal habitat variable called temperature at 3 mgÁL -1 of dissolved oxygen (T DO3 ) was developed by interpolating the water temperature at a benchmark oxygen concentration (3 mgÁL -1 ) from a temperature-oxygen profile. Coldwater habitat was most available in the least productive lakes (total P < 25 mgÁL -1 ) with the greatest relative depths (geometry ratios < 2 m -0.5 ) and where mean July air temperatures were less than 17 8C. Species response curves were developed from values of TDO3 measured during the greatest period of oxythermal stress in late summer (maxTDO3). Lake trout was present in lakes with the lowest values of maxTDO3, while cisco was present in lakes with the highest and broadest range of maxTDO3. Projections for a scenario where climate warming (+4 8C in mean July air temperature) was accompanied by eutrophication (doubling of total P) indicated that coldwater fish oxythermal habitat would be devastated in a subset of lakes typical for Minnesota. Protecting deep, unproductive lakes from eutrophication will be a necessary management strategy to ensure that coldwater fish persist in at least some Minnesota lakes after climate warming.Résumé : Nous mettons au point un modèle empirique qui décrit l'effet de la productivité lacustre, du climat et de la morphométrie sur l'habitat oxythermique des poissons d'eau froide. En interpolant la température de l'eau à une concentration repère d'oxygène (3 mgÁL -1 ) dans un profil de température-oxygène, nous obtenons une variable de l'habitat oxythermique, soit la température à 3 mgÁL -1 d'oxygène dissous (TDO3). L'habitat d'eau froide se retrouve le plus couramment dans les lacs les moins productifs (P total < 25 mgÁL -1 ) avec les profondeurs relatives les plus grandes (rapports géométri-ques < 2 m -0,5 ) et une température moyenne de l'air en juillet de moins de 17 8C. Nous avons mis au point des courbes de réaction des espèces à partir des valeurs de TDO3 mesurées durant la période de stress thermique maximal en fin d'été (TDO3 maximum). Les touladis se retrouvent dans les lacs qui ont les valeurs les plus basses de TDO3 maximum, alors que les ciscos vivent dans les lacs avec les étendues des valeurs de TDO3 maximum les plus élevées et les plus larges. Des projections selon un scénario dans lequel le réchauffement du climat (+4 8C de température moyenne de l'air en juillet) est accompagné d'une eutrophisation (dédoublement du P total) indiquent que l'habitat oxythermique des poissons d'eau froide serait dévasté dans un sous-ensemble de lacs typiques du Minnesota. Il sera nécessaire d'adopter une stratégie de gestion pour protéger les lacs profonds et peu productifs de l'eutrophisation afin d'assurer que les poissons d'eau froide survivent au moins dans certains lacs du Minnesota après le réchauffement climatique.[Traduit par la Rédaction]

Simulation and Validation of Cisco Lethal Conditions in Minnesota Lakes under Past and Future Climate Scenarios Using Constant Survival Limits

“…The LT = 23.4˝C [24] used for the cold-water fish guild in previous studies [14,26] was the mean value of LT values for ten cold-water fish species (pink salmon, sockeye salmon, chinook salmon, chum salmon, coho salmon, brown trout, rainbow trout, brook trout, lake trout, and mountain whitefish). Jacobson et al [4] The DO concentration of 3.0 mg/L requirement for the cold-water fish guild, below which mortality is more likely to occur or growth is impaired [27], was developed from an available US EPA database [28]. Jacobson et al [29] proposed a single oxythermal variable TDO3, and TDO3 is defined as the water temperature at 3 mg/L of DO.…”

“…Jacobson et al [4] developed a lethal oxythermal niche boundary curve (equation) for adult cisco. The curve mapped the temperatures and DO concentrations from the profiles measured in 17 Minnesota lakes ( The DO concentration of 3.0 mg/L requirement for the cold-water fish guild, below which mortality is more likely to occur or growth is impaired [27], was developed from an available US EPA database [28]. Jacobson et al [29] proposed a single oxythermal variable TDO3, and TDO3 is defined as the water temperature at 3 mg/L of DO.…”

Refuge Lake Reclassification in 620 Minnesota Cisco Lakes under Future Climate Scenarios

“…When a lake is classified as Tier 3 non-refuge lakes, it does not mean the lake cannot support cisco at all; only oxythermal stress to ciscoes are relatively high. Except for Lake Carlos, average three-day TDO3 before the cisco mortality date in 2006 in 17 lakes ranged from 19.0 to 26.2 • C (Table 6), which indicates the adult cisco kill temperature at DO = 3 mg/L was much higher than 17 • C. As Jacobson et al [25] stated, therefore, ciscoes can persist in lakes with TDO3 > 17 • C but at a reduced probability of occurrence.…”

“…When TDO3 is high, a lake only has suitable oxygen available at high water temperatures, likely at the shallower depths often within the metalimnion or epilimnion when hypolimnion is hypoxic; this represents poor oxythermal habitat [23]. TDO3 was originally proposed and used by Jacobson et al [25] to study oxythermal habitat of burbot (Lota lota), cisco, lake trout (Salvelinus namaycush), and lake whitefish (Coregonus clupeaformis), and which was connected and correlated with total phosphorus, summer air temperature, and relative depth of lakes. Multiyear average TDO3 simulated in 30 deep virtual lakes (maximum depth H max = 24 m) were used to identify and classify 620 Minnesota cisco lakes into three tiers of refuge lakes [10,12].…”

“…From the analysis of measured T and DO profiles, Jacobson et al [25] concluded that the highest probability of cisco occurrence was at a late-summer TDO3 of 9.0 • C, and the central species response borders ranged from 4.0 to 16.9 • C. To identify which lake is an acceptable cisco refuge lake, limits of TDO3 had to be specified. The criteria to select cisco refuge lakes used by Fang et al [12] and Jiang et al [10] were: (1) the Tier 1 refuge lake has AvgATDO3 VB < 11 • C (the subscript VB stands for variable benchmark period); (2) the Tier 2 refuge lake has 11 • C ≤ AvgATDO3 VB ≤ 17 • C ≥ 11 • C and ≤ 17 • C; and (3) the non-refuge lake has AvgATDO3 VB > 17 • C.…”