1 The following supplements accompany the article Transplantation as a conservation action to protect the Mediterranean fan mussel Pinna nobilis Stelios Katsanevakis* Corresponding author: [email protected]Marine Ecology Progress Series 546: 113–122 (2016) Supplement 1 Fig. S1: Map of the case study area. All experimental work as well as the developed matrix population model refer to Lake Vouliagmeni in Korinthiakos Gulf, Greece. The area where the transplantation experiments took place is outline with a red rectangle.
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The following supplements accompany the article
Transplantation as a conservation action to protect the Mediterranean fan mussel Pinna nobilis
Marine Ecology Progress Series 546: 113–122 (2016)
Supplement 1
Fig. S1: Map of the case study area. All experimental work as well as the developed matrix population model refer to Lake Vouliagmeni in Korinthiakos Gulf, Greece. The area where the transplantation experiments took place is outline with a red rectangle.
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Supplement 2. Justification of using a time-invariant population model to project the fan mussel population in Lake Vouliagmeni under various scenarios of transplantation
To demonstrate the potential effect of transplantation of fan mussels at population level, a metapopulation, time-invariant, stage-classified matrix model was applied. The model had been previously developed to assess the dynamics of the P. nobilis population in Lake Vouliagmeni (Katsanevakis 2009a). It has to be stressed that this linear, time-invariant model was used to project what would happen in the P. nobilis population, given certain hypotheses, and not to forecast what will happen in the future. As Caswell (2001) stresses: “forecasting uses the indicative mood and projection the subjunctive”. Ecological use of this purely analytical result (i.e. of a projection and not of a forecast) is sometimes criticized as if it asserted that the environment is constant. No such assumption is required to interpret the vital rates and population structure as answers to the hypothetical question: how would the population behave if the present conditions were to be maintained indefinitely (Caswell 2001)? Population projections reveal information about the relation between present conditions and the population experiencing them, not about the future behaviour of the population. Such information is valuable with a comparative approach as the one applied in this study, in which the population is projected under different conditions (in this case the application of varying levels of transplantation).
Scenarios based on a time-variant model, also accounting for density-dependence of fertilities, could provide additional insights, although they would be beyond the scope of this study. However, (1) there are no data available to estimate temporal variation, and thus any such analysis would be purely theoretical, and (2) density dependence seems of less importance as the population is at relative low abundance. The latter is supported by two arguments: (I) the average population density estimated in Lake Vouliagmeni is of the order of magnitude of a few individuals per 1000 m2, while much higher average densities have been recorded in the Mediterranean – of one to two orders of magnitude higher (see Table S1). A population density of a few individuals per 1000 m2 seems unlikely to exhibit substantial density dependence effects, e.g. higher mortality of larvae due to filtration by adults or high mortality/reduced growth of juveniles at high densities. (II) In Lake Vouliagmeni there is evidence of very high population densities in the past (see Fig. S2), ~3-4 orders of magnitude higher than the current population densities, i.e. of thousands or tens of thousands individuals per 1000 m2. This indicates that the current level of population density is much lower than the currying capacity of the lake.
On the other hand, reproductive success depends on the proximity of other individuals spawning synchronously. When a population becomes sparse, as is the case for most fan mussel populations, failure of fertilization could be a critical issue for the survival of the species. As the transplants could be concentrated into dense patches, higher fertilization success is probable, and thus the positive impact of transplantation actions on fan mussel populations could be greater than predicted by the model due to higher fertilization and increased recruitment.
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Table S1: Average population densities of Pinna nobilis, in various Mediterranean sites (modified from Rouanet et al. 2015)
Location
Average population density (individuals / 1000 m2) References
Port-Cros Island (Port-Cros National Park, MPA), Provence, France
10 Vicente et al. 1980; Combelles et al. 1986
Scandola marine reserve (MPA), Corsica 10 Combelles et al. 1986
Croatia, Adriatic Sea 90 Zavodnik et al. 1991
Chafarinas Islands, Spain, Northern Africa 32 Guallart 2000
Tunisia (east and southeast coast) 15 Rabaoui et al. 2010
Pass between Bagaud and Port-Cros Islands (Port-Cros National Park, MPA), Provence, France
60-130 Rouanet et al. 2012
Embiez Island, Six-Fours-les-Plages, Provence, France
19 Trigos et al. 2013
Javea, Alicante, Spain <10 García-March, pers. comm. (men-tioned in Rouanet et al. 2015)
Moraira, Alicante, Spain 10-120 García-March, pers. comm. (men-tioned in Rouanet et al. 2015)
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Fig. S2: In the past, very high population densities of Pinna nobilis led to the creation of biogenic hard substrate in many sites in Lake Vouliagmeni. The fan mussel population was so dense that it was possible for calcareous epifauna to merge and create a compact hard layer, converting sandy bottoms to hard biogenic reefs. In the top left picture a segment of such a biogenic reef can be seen. The same segment is turned upside down (top right) and remains of fan mussel individuals can be seen protruding below the hard surface. Another segment excavated from the sea floor is shown in the bottom pictures, where the high density of fan mussels is clearly visible. Photos: Y. Issaris
LITERATURE CITED
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Supplement 3.
Figure S3: Relative growth rates of P. nobilis individuals estimated as the increase in shell width during one year divided by the initial width, as a function of initial width. Relative growth rates are shown for three populations: transplanted individuals at a depth of 12 m; control, i.e. non-transplanted individuals at a depth of 12 m, monitored during the same period than the transplanted population; and control (old), i.e. non-transplanted individuals at depths between 9-12 m, monitored at an earlier time interval in another study (Katsanevakis 2007a).
