Kelps across the portuguese coast: evidence of top-down and bottom-up influences
Joao
N.
Franco1, 2*,
Thomas
Wernberg3,
Iacopo
Bertocci2,
Francisco
Arenas2,
Brezo
Martínez4,
Pedro
Duarte5,
David
Jacinto6,
Nuno
Vasco-Rodrigues7,
Isabel
Sousa-Pinto1, 2 and
Fernando
Tuya8
-
1
Department of Biology, Faculty of Sciences, University of Porto., Portugal
-
2
(CIIMAR/CIMAR) - Interdisciplinary Centre of Marine and Environmental Research , Portugal
-
3
UWA Oceans Institute & School of Plant Biology, Australia
-
4
Rey Juan Carlos University, Spain
-
5
Norwegian Polar Institute, Norway
-
6
Laboratório de Ciências do Mar , Universidade de Évora, Portugal
-
7
GIRM - Marine Resources Research Group, Polytecnic Institute of Leiria, Portugal
-
8
BIOGES, Universidad de Las Palmas de Gran Canaria, Spain
Kelps (large brown seaweeds) are conspicuous elements of the Portuguese coast, although kelp abundance is declining, especially at central and southern Portugal. While many studies point out increased seawater temperature as the main factor explaining kelp decline, little attention has been given to top-down (predatory) influences. Through in situ experiments, we tested how herbivory affects the distribution and abundance of kelp recruits. We compared the abundance and survivorship of recruits, the intensity of grazing on recruits and the abundance of herbivores between Viana do Castelo (northern Portugal) and Peniche (central Portugal). In addition, through an outdoor mesocosm experiment, we disentangled the independent and interactive effects of both seawater temperature and nutrients on kelp recruits performance (mortality, growth, C, N and carbohydrate contents, and photosynthetic potential and efficiency). Our main results showed that herbivores and herbivory intensity is higher at central compared to northern Portugal and that the growth of juvenile sporophytes was larger under a high-nutrient scenarios, particularly when temperatures were low (12, 15 and 16ºC). Despite the presence and fitness of kelps across southern European waters has been exclusively linked to bottom-up influences, our results highlights the importance of top-down effects for kelp survivorship and performance.
Acknowledgements
Financial support was provided by the ‘Programa Operacional Factores de Competitividade’ (POFC-COMPETE) within the Portuguese Fundação para a Ciência e a Tecnologia (FCT) through the projects ‛Efeitos do clima oceânico na macroecologia e resiliência a perturbações dos povoamentos de kelps’ - OCEANKELP (PTDC/MAR/109954/2009) and a PhD grant (SFRH/BD/84933/2012) to J. N. Franco. We thank Prof. Paulo Maranhão and ‘Escola Superior de Tecnologias do Mar – Instituto Politecnico de Leiria’ (ESTM –IPL)
Keywords:
Climate Change,
Herbivory,
Nutrients,
temperature,
latitudinal gradient,
rocky reefs
Conference:
IMMR | International Meeting on Marine Research 2014, Peniche, Portugal, 10 Jul - 11 Jul, 2014.
Presentation Type:
Oral Presentation
Topic:
BIODIVERSITY, CONSERVATION AND COASTAL MANAGEMENT
Citation:
Franco
JN,
Wernberg
T,
Bertocci
I,
Arenas
F,
Martínez
B,
Duarte
P,
Jacinto
D,
Vasco-Rodrigues
N,
Sousa-Pinto
I and
Tuya
F
(2014). Kelps across the portuguese coast: evidence of top-down and bottom-up influences.
Front. Mar. Sci.
Conference Abstract:
IMMR | International Meeting on Marine Research 2014.
doi: 10.3389/conf.fmars.2014.02.00086
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Received:
14 Apr 2014;
Published Online:
18 Jul 2014.
*
Correspondence:
Mr. Joao N Franco, Department of Biology, Faculty of Sciences, University of Porto., Porto, Portugal, joaonunofranco@gmail.com