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Ecological Change, Sliding Baselines and the Importance of Historical Data: Lessons from Combing Observational and Quantitative Data on a Temperate Reef Over 70 Years

View Article: PubMed Central - PubMed

ABSTRACT

Understanding the effects of environmental change on ecosystems requires the identification of baselines that may act as reference conditions. However, the continuous change of these references challenges our ability to define the true natural status of ecosystems. The so-called sliding baseline syndrome can be overcome through the analysis of quantitative time series, which are, however, extremely rare. Here we show how combining historical quantitative data with descriptive ‘naturalistic’ information arranged in a chronological chain allows highlighting long-term trends and can be used to inform present conservation schemes. We analysed the long-term change of a coralligenous reef, a marine habitat endemic to the Mediterranean Sea. The coralligenous assemblages of Mesco Reef (Ligurian Sea, NW Mediterranean) have been studied, although discontinuously, since 1937 thus making available both detailed descriptive information and scanty quantitative data: while the former was useful to understand the natural history of the ecosystem, the analysis of the latter was of paramount importance to provide a formal measure of change over time. Epibenthic assemblages remained comparatively stable until the 1990s, when species replacement, invasion by alien algae, and biotic homogenisation occurred within few years, leading to a new and completely different ecosystem state. The shift experienced by the coralligenous assemblages of Mesco Reef was probably induced by a combination of seawater warming and local human pressures, the latter mainly resulting in increased water turbidity; in turn, cumulative stress may have favoured the establishment of alien species. This study showed that the combined analysis of quantitative and descriptive historical data represent a precious knowledge to understand ecosystem trends over time and provide help to identify baselines for ecological management.

No MeSH data available.


Related in: MedlinePlus

Ordination plot on the first three axes (Roman numerals) from Correspondence Analysis of the cover data matrix for the coralligenous assemblages of Mesco Reef, from 1961 to 2008.The upper left panel depicts the plot of all species points (crosses) and photoquadrat points (dots) to show the overall geometry of the ordination model. Details for each site are illustrated separately for the sake of clarity in the subsequent five panels, clockwise: trajectory and species of the assemblage at site B; trajectory and species of the assemblage at site C; trajectory and species of the assemblage at site D; trajectory and species of the assemblage at site F; trajectory and species of the assemblage at site I; position in 1961 and species of the assemblage at site P; trajectory and species of the assemblage at site S. Codes refer to the name of the species as showed in Table 1.
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pone.0118581.g005: Ordination plot on the first three axes (Roman numerals) from Correspondence Analysis of the cover data matrix for the coralligenous assemblages of Mesco Reef, from 1961 to 2008.The upper left panel depicts the plot of all species points (crosses) and photoquadrat points (dots) to show the overall geometry of the ordination model. Details for each site are illustrated separately for the sake of clarity in the subsequent five panels, clockwise: trajectory and species of the assemblage at site B; trajectory and species of the assemblage at site C; trajectory and species of the assemblage at site D; trajectory and species of the assemblage at site F; trajectory and species of the assemblage at site I; position in 1961 and species of the assemblage at site P; trajectory and species of the assemblage at site S. Codes refer to the name of the species as showed in Table 1.

Mentions: A total of 53 sessile conspicuous species, belonging to seven higher taxa, was recognised on photoquadrats between 1961–62 and 2008 (Table 1). Sponges were the richest group (20 species), followed by cnidarians (13) and bryozoans (7); the remaining groups were less represented (rhodophytes with 5 species, chlorophytes and polychaetes with 3 species each, and tunicates with 2 species).


Ecological Change, Sliding Baselines and the Importance of Historical Data: Lessons from Combing Observational and Quantitative Data on a Temperate Reef Over 70 Years
Ordination plot on the first three axes (Roman numerals) from Correspondence Analysis of the cover data matrix for the coralligenous assemblages of Mesco Reef, from 1961 to 2008.The upper left panel depicts the plot of all species points (crosses) and photoquadrat points (dots) to show the overall geometry of the ordination model. Details for each site are illustrated separately for the sake of clarity in the subsequent five panels, clockwise: trajectory and species of the assemblage at site B; trajectory and species of the assemblage at site C; trajectory and species of the assemblage at site D; trajectory and species of the assemblage at site F; trajectory and species of the assemblage at site I; position in 1961 and species of the assemblage at site P; trajectory and species of the assemblage at site S. Codes refer to the name of the species as showed in Table 1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4340909&req=5

pone.0118581.g005: Ordination plot on the first three axes (Roman numerals) from Correspondence Analysis of the cover data matrix for the coralligenous assemblages of Mesco Reef, from 1961 to 2008.The upper left panel depicts the plot of all species points (crosses) and photoquadrat points (dots) to show the overall geometry of the ordination model. Details for each site are illustrated separately for the sake of clarity in the subsequent five panels, clockwise: trajectory and species of the assemblage at site B; trajectory and species of the assemblage at site C; trajectory and species of the assemblage at site D; trajectory and species of the assemblage at site F; trajectory and species of the assemblage at site I; position in 1961 and species of the assemblage at site P; trajectory and species of the assemblage at site S. Codes refer to the name of the species as showed in Table 1.
Mentions: A total of 53 sessile conspicuous species, belonging to seven higher taxa, was recognised on photoquadrats between 1961–62 and 2008 (Table 1). Sponges were the richest group (20 species), followed by cnidarians (13) and bryozoans (7); the remaining groups were less represented (rhodophytes with 5 species, chlorophytes and polychaetes with 3 species each, and tunicates with 2 species).

View Article: PubMed Central - PubMed

ABSTRACT

Understanding the effects of environmental change on ecosystems requires the identification of baselines that may act as reference conditions. However, the continuous change of these references challenges our ability to define the true natural status of ecosystems. The so-called sliding baseline syndrome can be overcome through the analysis of quantitative time series, which are, however, extremely rare. Here we show how combining historical quantitative data with descriptive ‘naturalistic’ information arranged in a chronological chain allows highlighting long-term trends and can be used to inform present conservation schemes. We analysed the long-term change of a coralligenous reef, a marine habitat endemic to the Mediterranean Sea. The coralligenous assemblages of Mesco Reef (Ligurian Sea, NW Mediterranean) have been studied, although discontinuously, since 1937 thus making available both detailed descriptive information and scanty quantitative data: while the former was useful to understand the natural history of the ecosystem, the analysis of the latter was of paramount importance to provide a formal measure of change over time. Epibenthic assemblages remained comparatively stable until the 1990s, when species replacement, invasion by alien algae, and biotic homogenisation occurred within few years, leading to a new and completely different ecosystem state. The shift experienced by the coralligenous assemblages of Mesco Reef was probably induced by a combination of seawater warming and local human pressures, the latter mainly resulting in increased water turbidity; in turn, cumulative stress may have favoured the establishment of alien species. This study showed that the combined analysis of quantitative and descriptive historical data represent a precious knowledge to understand ecosystem trends over time and provide help to identify baselines for ecological management.

No MeSH data available.


Related in: MedlinePlus