Life history constraints explain negative relationship between fish productivity and dissolved organic carbon in lakes

Abstract

Resource availability constrains the life history strategies available to organisms and may thereby limit population growth rates and productivity. We used this conceptual framework to explore the mechanisms driving recently reported negative relationships between fish productivity and dissolved organic carbon (DOC) concentrations in lakes. We studied populations of bluegill (Lepomis macrochirus) in a set of lakes with DOC concentrations ranging from 3 to 24 mg/L; previous work has demonstrated that primary and secondary productivity of food webs is negatively related to DOC concentration across this gradient. For each population, we quantified individual growth rate, age at maturity, age‐specific fecundity, maximum age, length‐weight and length‐egg size relationships, and other life history characteristics. We observed a strong negative relationship between maximum size and DOC concentration; for instance, fish reached masses of 150 to 260 g in low‐DOC lakes but <120 g in high‐DOC lakes. Relationships between fecundity and length, and between egg size and length, were constant across the DOC gradient. Because fish in high‐DOC lakes reached smaller sizes but had similar fecundity and egg size at a given size, their total lifetime fecundity was as much as two orders of magnitude lower than fish in low‐DOC lakes. High DOC concentrations appeared to constrain the range of bluegill life history strategies available; populations in high‐DOC lakes always had low initial growth rates and high ages at maturity, whereas populations in low‐DOC showed higher variability in these traits. This was also the case for the intrinsic rates of natural increase of these populations, which were always low at the high end of the DOC gradient. The potentially lower capacity for fish populations in high‐DOC lakes to recover from exploitation has clear implications for the sustainable management of recreational fisheries in the face of considerable spatial heterogeneity and ongoing temporal change in lake DOC concentrations.

Fewer blue lakes and more murky lakes across the continental U.S.: Implications for planktonic food webs

“…Karlsson et al () noted a decrease in fish biomass with increasing lake DOC concentration, which they equated with an increase in lake color. Similarly, Craig et al () recently reported that bluegill from humic lakes were smaller in body size and had reduced fecundity compared to those in clear lakes. Taipale et al () noted that perch from lakes with high phosphorus and dissolved organic carbon concentrations generally had smaller body sizes, which correlated with lower concentrations of nutritional EPA and DHA fatty acids.…”

Global change‐driven effects on dissolved organic matter composition: Implications for food webs of northern lakes

“…The role of allochthonous inputs of DOM as the trophic basis of lake productivity remains contested, and our review has pointed to some conflicting literature findings. Survey results indicate that browning tends to reduce productivity at primary and higher trophic levels (e.g., Craig, Jones, Weidel, & Solomon, ; Kelly et al., ), but recent experimental manipulations of DOM inputs (albeit a smaller concentration increase than the surveys encompassed) showed a positive impact on both phytoplankton and zooplankton productivity (Kelly et al., ; Zwart et al., ). Conflicting results highlight the need for more experimental studies, improved understanding of the link between DOM and changes in light and nutrient availability, and documentation of contexts that may condition the response to DOM inputs.…”

The browning and re-browning of lakes: Divergent lake-water organic carbon trends linked to acid deposition and climate change

“…For example, DOC affects light attenuation, oxygen and nutrient availability, and consequently the development of thermal stratification and hypoxia as well as species distributions and habitat availability 4,5 . Examples of chemical and biological repercussions of the current browning trend include reduced fish growth 6,7 , more favourable conditions for toxin-producing cyanobacteria blooms 8 , reduced potential for the inactivation of pathogens by solar ultraviolet radiation 9 , and increased contaminant transport 10,11 .…”