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Consumers control diversity and functioning of a natural marine ecosystem.

Altieri AH, Trussell GC, Ewanchuk PJ, Bernatchez G, Bracken ME - PLoS ONE (2009)

Bottom Line: Seaweed species evenness and biomass-specific primary productivity (mg O(2) h(-1) g(-1)) were higher in tide pools with snails because snails preferentially consumed an otherwise dominant seaweed species that can reduce biomass-specific productivity rates of algal assemblages.Although snails reduced overall seaweed biomass in tide pools, they did not affect gross primary productivity at the scale of tide pools (mg O(2) h(-1) pool(-1) or mg O(2) h(-1) m(-2)) because of the enhanced biomass-specific productivity associated with grazer-mediated increases in algal evenness.Our results suggest that increased attention to trophic interactions, diversity measures other than richness, and particularly the effects of consumers on evenness and primary productivity, will improve our understanding of the relationship between diversity and ecosystem functioning and allow more effective links between experimental results and real-world changes in biodiversity.

View Article: PubMed Central - PubMed

Affiliation: Marine Science Center, Northeastern University, Nahant, Massachusetts, United States of America.

ABSTRACT

Background: Our understanding of the functional consequences of changes in biodiversity has been hampered by several limitations of previous work, including limited attention to trophic interactions, a focus on species richness rather than evenness, and the use of artificially assembled communities.

Methodology and principal findings: In this study, we manipulated the density of an herbivorous snail in natural tide pools and allowed seaweed communities to assemble in an ecologically relevant and non-random manner. Seaweed species evenness and biomass-specific primary productivity (mg O(2) h(-1) g(-1)) were higher in tide pools with snails because snails preferentially consumed an otherwise dominant seaweed species that can reduce biomass-specific productivity rates of algal assemblages. Although snails reduced overall seaweed biomass in tide pools, they did not affect gross primary productivity at the scale of tide pools (mg O(2) h(-1) pool(-1) or mg O(2) h(-1) m(-2)) because of the enhanced biomass-specific productivity associated with grazer-mediated increases in algal evenness.

Significance: Our results suggest that increased attention to trophic interactions, diversity measures other than richness, and particularly the effects of consumers on evenness and primary productivity, will improve our understanding of the relationship between diversity and ecosystem functioning and allow more effective links between experimental results and real-world changes in biodiversity.

Show MeSH
Influence of seaweed species evenness on biomass-specific productivity in tide pools.The positive relationship between biomass-specific productivity and seaweed species evenness (P = 0.001) held even after accounting for the potential effects of biomass variation on productivity (see Results). Symbols indicate pools of different snail densities: 0 per m2 (circles), 150 per m2 (triangles), and 250 per m2 (squares).
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pone-0005291-g002: Influence of seaweed species evenness on biomass-specific productivity in tide pools.The positive relationship between biomass-specific productivity and seaweed species evenness (P = 0.001) held even after accounting for the potential effects of biomass variation on productivity (see Results). Symbols indicate pools of different snail densities: 0 per m2 (circles), 150 per m2 (triangles), and 250 per m2 (squares).

Mentions: Grazing by snails increased tide pool seaweed species evenness (P = 0.05, Table S1, Fig. 1A) and biomass (g m−2; P<0.001, Table S1, Fig. 1B). Increases in snail density were also associated with enhanced biomass-specific productivity (mg O2 h−1 g−1) of tide pool macroalgae (P = 0.01, Table S2, Fig. 1C). This result was not due to snail respiration, because we found no relationship between snail density and respiration (O2 consumption) rates in tide pools (F1,20 = 0.007, P = 0.933). Even after accounting for the inhibiting effect of algal biomass (g/L) on biomass-specific productivity (F1,19 = 20.7, P<0.001), there was a positive relationship between algal species evenness and biomass-specific productivity (F1,19 = 15.0, P = 0.001; Fig. 2). Due to this grazer-mediated enhancement of biomass-specific productivity, snails had no effect on whole tide pool gross productivity (P = 0.22, Table S2) or area-specific productivity (P = 0.47, Table S2), despite their reduction of algal standing crop biomass.


Consumers control diversity and functioning of a natural marine ecosystem.

Altieri AH, Trussell GC, Ewanchuk PJ, Bernatchez G, Bracken ME - PLoS ONE (2009)

Influence of seaweed species evenness on biomass-specific productivity in tide pools.The positive relationship between biomass-specific productivity and seaweed species evenness (P = 0.001) held even after accounting for the potential effects of biomass variation on productivity (see Results). Symbols indicate pools of different snail densities: 0 per m2 (circles), 150 per m2 (triangles), and 250 per m2 (squares).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2668074&req=5

pone-0005291-g002: Influence of seaweed species evenness on biomass-specific productivity in tide pools.The positive relationship between biomass-specific productivity and seaweed species evenness (P = 0.001) held even after accounting for the potential effects of biomass variation on productivity (see Results). Symbols indicate pools of different snail densities: 0 per m2 (circles), 150 per m2 (triangles), and 250 per m2 (squares).
Mentions: Grazing by snails increased tide pool seaweed species evenness (P = 0.05, Table S1, Fig. 1A) and biomass (g m−2; P<0.001, Table S1, Fig. 1B). Increases in snail density were also associated with enhanced biomass-specific productivity (mg O2 h−1 g−1) of tide pool macroalgae (P = 0.01, Table S2, Fig. 1C). This result was not due to snail respiration, because we found no relationship between snail density and respiration (O2 consumption) rates in tide pools (F1,20 = 0.007, P = 0.933). Even after accounting for the inhibiting effect of algal biomass (g/L) on biomass-specific productivity (F1,19 = 20.7, P<0.001), there was a positive relationship between algal species evenness and biomass-specific productivity (F1,19 = 15.0, P = 0.001; Fig. 2). Due to this grazer-mediated enhancement of biomass-specific productivity, snails had no effect on whole tide pool gross productivity (P = 0.22, Table S2) or area-specific productivity (P = 0.47, Table S2), despite their reduction of algal standing crop biomass.

Bottom Line: Seaweed species evenness and biomass-specific primary productivity (mg O(2) h(-1) g(-1)) were higher in tide pools with snails because snails preferentially consumed an otherwise dominant seaweed species that can reduce biomass-specific productivity rates of algal assemblages.Although snails reduced overall seaweed biomass in tide pools, they did not affect gross primary productivity at the scale of tide pools (mg O(2) h(-1) pool(-1) or mg O(2) h(-1) m(-2)) because of the enhanced biomass-specific productivity associated with grazer-mediated increases in algal evenness.Our results suggest that increased attention to trophic interactions, diversity measures other than richness, and particularly the effects of consumers on evenness and primary productivity, will improve our understanding of the relationship between diversity and ecosystem functioning and allow more effective links between experimental results and real-world changes in biodiversity.

View Article: PubMed Central - PubMed

Affiliation: Marine Science Center, Northeastern University, Nahant, Massachusetts, United States of America.

ABSTRACT

Background: Our understanding of the functional consequences of changes in biodiversity has been hampered by several limitations of previous work, including limited attention to trophic interactions, a focus on species richness rather than evenness, and the use of artificially assembled communities.

Methodology and principal findings: In this study, we manipulated the density of an herbivorous snail in natural tide pools and allowed seaweed communities to assemble in an ecologically relevant and non-random manner. Seaweed species evenness and biomass-specific primary productivity (mg O(2) h(-1) g(-1)) were higher in tide pools with snails because snails preferentially consumed an otherwise dominant seaweed species that can reduce biomass-specific productivity rates of algal assemblages. Although snails reduced overall seaweed biomass in tide pools, they did not affect gross primary productivity at the scale of tide pools (mg O(2) h(-1) pool(-1) or mg O(2) h(-1) m(-2)) because of the enhanced biomass-specific productivity associated with grazer-mediated increases in algal evenness.

Significance: Our results suggest that increased attention to trophic interactions, diversity measures other than richness, and particularly the effects of consumers on evenness and primary productivity, will improve our understanding of the relationship between diversity and ecosystem functioning and allow more effective links between experimental results and real-world changes in biodiversity.

Show MeSH