HERBIVORY
Carol Thornber
Department of Biological Sciences, University of Rhode
Island, Kingston, RI, USA
Synonyms
Grazing
Definition
Herbivory is a type of exploitation in which heterotrophs
consume autotroph (algae and plants) biomass.
Summary
Herbivory is common and widespread in estuarine systems, and numerous invertebrate and vertebrate taxa can
act as herbivores in these habitats (see Herbivorous
Grazers).
Estuaries worldwide vary substantially in herbivore
densities and consumption rates, leading to corresponding
variation in the trophic impact and ecosystem-level importance of herbivory. Herbivory can shape the abundance,
distribution, and species composition of primary producers. Herbivores in low-nutrient systems can serve as
a “biological control” for algal blooms, for example, but
may have little impact on algal biomass under other conditions (Hauxwell et al., 1998; Worm and Lotze, 2006).
In many estuarine systems, primary producer biomass is
mainly degraded via detrital pathways, with herbivory
having a much more limited role (e.g., Conover, 2011;
Guidone et al., 2012).
In systems where herbivory plays an important role,
primary producers frequently utilize morphological adaptations and/or produce secondary metabolites as defenses
against consumers. Morphological adaptations include
spines, scales, or thick and tough outer tissue layers, while
secondary metabolites can make plants and algae distasteful or toxic to grazers (Hay et al., 1994; Van Alstyne et al.,
2007).
Bibliography
Conover, J., 2011. Variability in Biomass Decay Rates and Nutrient
Loss in Bloom-Forming Macroalgal Species. Open Access
Masters' Theses, Paper 108, University of Rhode Island,
Kingston, RI.
Guidone, M., Thornber, C. S., and Vincent, E., 2012. Snail grazing
facilitates growth of two morphologically similar bloom forming
Ulva species through different mechanisms. Journal of Ecology,
100, 1105–1112.
Hauxwell, J., McClelland, J., Behr, P. J., and Valiela, I., 1998.
Relative importance of grazing and nutrient controls of
macroalgal biomass in three temperate shallow estuaries.
Estuaries, 21, 347–360.
Hay, M. E., Kappel, Q. E., and Fenical, W., 1994. Synergisms in
plant defenses against herbivores: interactions of chemistry,
calcification, and plant quality. Ecology, 75, 1714–1726.
Van Alstyne, K. L., Koellermeir, L., and Nelson, T. A., 2007. Spatial
variation in dimethylsulfoniopropionate (DMSP) production in
Ulva lactuca (Chlorophyta) from the Northeast Pacific. Marine
Biology, 150, 1127–1135.
Worm, B., and Lotze, H. K., 2006. Effects of eutrophication, grazing, and algal blooms on rocky shores. Limnology and Oceanography, 51, 569–579.
Cross-references
Ecological Niche
Food Web/Trophic Dynamics
Herbivorous Grazers
HETEROTROPHIC
Antje Rusch
Department of Microbiology and Center for Ecology,
Southern Illinois University Carbondale, Carbondale,
IL, USA
Definition
Heterotrophic organisms use organic carbon compounds
for their carbon source (Okafar, 2011). The corresponding
pathways of carbon metabolism are also referred to as
heterotrophic.
Etymology: from Greek έterοB (other, different) and
Greek trοjή (nourishment).
To meet their cellular demand of carbon, heterotrophic
organisms rely on organic carbon compounds that originate from other organisms. Examples include animals,
fungi, numerous bacterial and archaeal species, and parasitic plants. The latter, however, have not been detected
in aquatic environments (Rubiales and Heide-Jørgensen,
2011). In addition, many autotrophic organisms can operate heterotrophic metabolic pathways. Heterotrophic bacteria and zooplankton are important players in the
microbial loop of aquatic food webs (Barber, 2007;
Fenchel, 2008).
Bibliography
Barber, R. T., 2007. Picoplankton do some heavy lifting. Science,
315, 777–778.
Fenchel, T., 2008. The microbial loop – 25 years later. Journal of
Experimental Marine Biology and Ecology, 366, 99–103.
Okafar, N., 2011. Environmental Microbiology of Aquatic and
Waste Systems. Dordrecht: Springer Netherlands.
Rubiales, D., and Heide-Jørgensen, H. S., 2011. Parasitic
plants. In Encyclopedia of Life Sciences. Chichester: Wiley.
http://www.els.net.
Cross-references
Autotrophic
Detritus Food Webs
Microbial Degradation
HETEROTROPHIC
357
Carol Thornber
Department of Biological Sciences, University of Rhode
Island, Kingston, RI, USA
Synonyms
Grazing
Definition
Herbivory is a type of exploitation in which heterotrophs
consume autotroph (algae and plants) biomass.
Summary
Herbivory is common and widespread in estuarine systems, and numerous invertebrate and vertebrate taxa can
act as herbivores in these habitats (see Herbivorous
Grazers).
Estuaries worldwide vary substantially in herbivore
densities and consumption rates, leading to corresponding
variation in the trophic impact and ecosystem-level importance of herbivory. Herbivory can shape the abundance,
distribution, and species composition of primary producers. Herbivores in low-nutrient systems can serve as
a “biological control” for algal blooms, for example, but
may have little impact on algal biomass under other conditions (Hauxwell et al., 1998; Worm and Lotze, 2006).
In many estuarine systems, primary producer biomass is
mainly degraded via detrital pathways, with herbivory
having a much more limited role (e.g., Conover, 2011;
Guidone et al., 2012).
In systems where herbivory plays an important role,
primary producers frequently utilize morphological adaptations and/or produce secondary metabolites as defenses
against consumers. Morphological adaptations include
spines, scales, or thick and tough outer tissue layers, while
secondary metabolites can make plants and algae distasteful or toxic to grazers (Hay et al., 1994; Van Alstyne et al.,
2007).
Bibliography
Conover, J., 2011. Variability in Biomass Decay Rates and Nutrient
Loss in Bloom-Forming Macroalgal Species. Open Access
Masters' Theses, Paper 108, University of Rhode Island,
Kingston, RI.
Guidone, M., Thornber, C. S., and Vincent, E., 2012. Snail grazing
facilitates growth of two morphologically similar bloom forming
Ulva species through different mechanisms. Journal of Ecology,
100, 1105–1112.
Hauxwell, J., McClelland, J., Behr, P. J., and Valiela, I., 1998.
Relative importance of grazing and nutrient controls of
macroalgal biomass in three temperate shallow estuaries.
Estuaries, 21, 347–360.
Hay, M. E., Kappel, Q. E., and Fenical, W., 1994. Synergisms in
plant defenses against herbivores: interactions of chemistry,
calcification, and plant quality. Ecology, 75, 1714–1726.
Van Alstyne, K. L., Koellermeir, L., and Nelson, T. A., 2007. Spatial
variation in dimethylsulfoniopropionate (DMSP) production in
Ulva lactuca (Chlorophyta) from the Northeast Pacific. Marine
Biology, 150, 1127–1135.
Worm, B., and Lotze, H. K., 2006. Effects of eutrophication, grazing, and algal blooms on rocky shores. Limnology and Oceanography, 51, 569–579.
Cross-references
Ecological Niche
Food Web/Trophic Dynamics
Herbivorous Grazers
HETEROTROPHIC
Antje Rusch
Department of Microbiology and Center for Ecology,
Southern Illinois University Carbondale, Carbondale,
IL, USA
Definition
Heterotrophic organisms use organic carbon compounds
for their carbon source (Okafar, 2011). The corresponding
pathways of carbon metabolism are also referred to as
heterotrophic.
Etymology: from Greek έterοB (other, different) and
Greek trοjή (nourishment).
To meet their cellular demand of carbon, heterotrophic
organisms rely on organic carbon compounds that originate from other organisms. Examples include animals,
fungi, numerous bacterial and archaeal species, and parasitic plants. The latter, however, have not been detected
in aquatic environments (Rubiales and Heide-Jørgensen,
2011). In addition, many autotrophic organisms can operate heterotrophic metabolic pathways. Heterotrophic bacteria and zooplankton are important players in the
microbial loop of aquatic food webs (Barber, 2007;
Fenchel, 2008).
Bibliography
Barber, R. T., 2007. Picoplankton do some heavy lifting. Science,
315, 777–778.
Fenchel, T., 2008. The microbial loop – 25 years later. Journal of
Experimental Marine Biology and Ecology, 366, 99–103.
Okafar, N., 2011. Environmental Microbiology of Aquatic and
Waste Systems. Dordrecht: Springer Netherlands.
Rubiales, D., and Heide-Jørgensen, H. S., 2011. Parasitic
plants. In Encyclopedia of Life Sciences. Chichester: Wiley.
http://www.els.net.
Cross-references
Autotrophic
Detritus Food Webs
Microbial Degradation
HETEROTROPHIC
357