Role of Fish in Structuring Invertebrates on Stromatolites in Cuatro Ciénegas, México

Abstract

Stromatolites, the dominant Precambrian life form, declined in the Phanerozoic to occur today in only a few sites. This decline has been attributed to evolution of metazoan grazers, but stromatolites in our study site, Cuatro Cie´negas, Coahuila, Me´xico, harbor diverse macroinvertebrates. Drawing on food chain theory, we hypothesized that fish predation on invertebrates controls invertebrate populations, allowing stromatolites to flourish in Cuatro Cie´negas. Our experiment used small mesh (1 mm) cages to exclude all but larval fishes, and larger (6.5 mm) cages to exclude all larger fishes (including the molluscivorous and omnivorous endemic polymorphic cichlid, Herichthys minckleyi), but allow access to all sizes of the abundant endemic pupfish, Cyprinodon bifasciatus. No effects of treatments on invertebrate densities were noted at 6 week, but significant effects were observed on specific taxonomic groups after 3 month. In absence of fishes, hydrobiidae snails and ceratopogonids increased 3-and 5-fold, respectively, and invertebrate assemblage composition varied among treatments. Algal biomass was not affected by treatments, but algal species composition appeared to change. Overall results suggest that fish assemblages structure invertebrate assemblages, and that fishes may also be factors in determining algal communities.

Coexisting living stromatolites and infaunal metazoans

“…2c). The micro-habitat characteristics of extant microbialites may, thereby, be providing localized respite for invertebrates from predation (Dinger et al 2006;Konishi et al 2001) and harsh physical conditions, as well as offering an oxygen refuge (Des Marais 2003;Gingras et al 2011;Herman and Kump 2005;Mobberley et al 2015). For example, in the South African stromatolite pools during the warmer months, anoxic events have been observed whereby a milky benthic layer with a distinctive hydrogen sulphide odor forms [oxygen concentrations as low as 0.24 mg L −1 , compared to supersaturated levels of up to 37.0 mg L −1 above the stromatolites (Perissinotto et al 2014;Rishworth et al 2016)], from which metazoans might use the adjacent stromatolite matrix as a temporary oxygen refuge during daylight hours.…”

Identifying origins of and pathways for spring waters in a semiarid basin using He, Sr, and C isotopes: Cuatrocienegas Basin, Mexico

“…Other springs are located at the base of alluvial fans (Wolaver and Diehl, 2011). CO 2 -rich spring water with pCO 2 1.5-3 orders of magnitude higher than atmosphere facilitates deposition of rare modern freshwater stromatolites (Dinger et al, 2006).…”

Winning the biodiversity arms race among freshwater gastropods: competition and coexistence through shell variability and predator avoidance

“…The size and types of bioherms vary from the large, complex forms and depth distributions observed in the larger and much deeper Lake Tanganyika to smaller forms in other basins such Laguna Chichancanab and Cuarto Cienegas in Mexico. The biologically built structures that occur in isolated desert springs of Cuarto Cienegas (Winsborough & Golubić, 1987;Dinger et al, 2006) have similar high concentrations of calcium sulfate to those observed in Chichancanab. These reef-like formations can dry out during low lake levels and then reform once the water levels rise; wave action can move them during storms and rounded forms sometimes form in shallow waters (Covich, personal observations).…”

“…In Chichancanab, crayfish excavate and hollow out the concretions and use them for refuge. Habitat structure influences how different predatory species search for food and defend feeding territories in the shallow littoral zones of lakes (e.g., Stevenson, 1992;Dinger et al, 2006;Horstkotte & Plath, 2008;Plath & Strecker, 2008).…”

“…Field experiments in Cuarto Cienegas, Mexico, demonstrate that hydrobid snails (such as Mexipyrgus churinceaus) increase threefold in density when predatory fishes (Herichthys mincleyi and Cyprinodon bifaciatus) were excluded (Dinger et al, 2006). In general, the evolution of endemic hydrobid snails is often characterized by a high degree of variability in shell thickness (Taylor, 1966;Hershler, 1984Hershler, , 1985 that was associated with the feeding by endemic molluscivorous fishes (Sage & Selander, 1975;Trapani, 2003;Hulsey et al, 2006;Johnson et al, 2007;Hulsey et al, 2008).…”