Bella S. GALIL, MIENIS H. K., MENDELSON M., GAYER K., GOREN M.
The Steinhardt Museum of Natural History and Israel National Center for Biodiversity
Studies, Tel Aviv University, Israel. Sciences
E-mail: bgalil@tauex.tau.ac.il
HERE TODAY, GONE TOMORROW – THE LEVANTINE
POPULATION OF THE BROWN MUSSEL PERNA PERNA
DECIMATED BY AN UNPRECEDENTED HEATWAVE
Abstract
The newly established population of Perna perna (Bivalvia, Mytilidae) surveyed at four sites
along the Israeli Mediterranean coast averaged between 2155 and 8022 specimens/m² in June
2021. The population suffered catastrophic mortality following a succession of heatwaves
culminating in a prolonged heatwave in August (ambient temperature 36 to 38 °C, sea surface
32 °C). Yet, as an opportunistic species, ecosystem engineer, and fouling threat with rapid
growth rate, the profuse presence of P. perna raised the possibility of ramifications for
intertidal community structure.
Key-words: Invasion, population size-frequency, marine heat wave, mortality
Introduction
The brown mussel Perna perna (Linnaeus, 1758), a widely invasive mytilid mussel,
was first reported from the Mediterranean coast of Israel in 1965. No living specimens
of P. perna were documented in Israel in the next 55 years. The first documented
evidence of the reappearance of P. perna along the Israeli coast consisted of
photographs of small densely packed mussel patches north of Haifa port taken in May
2020. Subsequent surveys conducted along the Israeli shore in summer 2020 revealed
patchy but dense aggregations at several locations. An opportunistic species, ecosystem
engineer, and fouling threat with rapid growth rate, the profuse presence of P. perna on
the Mediterranean Israeli coast raised the possibility of ramifications for intertidal
community structure.
The study set out to document and compare the status of P. perna population at four sites,
comprising basic data on population density, size structure, growth rate, and epibiota
within one year of their initial detection. The study plan was upended by an
unprecedented heatwave that annihilated the entire population at the sampled sites and
throughout the Israeli coastline.
Materials and methods
Samples for population size structure analyses were collected at four sites, spanning
approximately 140 km of coastline. Samples from Haifa A (32°49′59.4″N; 35°03′04.2″E) and
Ashdod B (31°44′49.5″N; 34°36′03.6″E) were collected from semi-isolated small rocky
outcrops separated by shallow troughs from public bathing beaches; from Ashdod A, a stretch
of beach rock situated north of Ashdod Port (31°51′16.5″N; 34°39′39.3″E) and from Haifa B,
concrete barrier blocks protecting the seaward fence of the Petroleum and Energy
Infrastructures (PEI) facility, adjacent to Haifa port (32°49′35.1″N; 35°02′42.8″E). Mussels
were scraped from within three randomly placed replicate 30 × 30 cm quadrates in June 2021.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
95
The Steinhardt Museum of Natural History and Israel National Center for Biodiversity
Studies, Tel Aviv University, Israel. Sciences
E-mail: bgalil@tauex.tau.ac.il
HERE TODAY, GONE TOMORROW – THE LEVANTINE
POPULATION OF THE BROWN MUSSEL PERNA PERNA
DECIMATED BY AN UNPRECEDENTED HEATWAVE
Abstract
The newly established population of Perna perna (Bivalvia, Mytilidae) surveyed at four sites
along the Israeli Mediterranean coast averaged between 2155 and 8022 specimens/m² in June
2021. The population suffered catastrophic mortality following a succession of heatwaves
culminating in a prolonged heatwave in August (ambient temperature 36 to 38 °C, sea surface
32 °C). Yet, as an opportunistic species, ecosystem engineer, and fouling threat with rapid
growth rate, the profuse presence of P. perna raised the possibility of ramifications for
intertidal community structure.
Key-words: Invasion, population size-frequency, marine heat wave, mortality
Introduction
The brown mussel Perna perna (Linnaeus, 1758), a widely invasive mytilid mussel,
was first reported from the Mediterranean coast of Israel in 1965. No living specimens
of P. perna were documented in Israel in the next 55 years. The first documented
evidence of the reappearance of P. perna along the Israeli coast consisted of
photographs of small densely packed mussel patches north of Haifa port taken in May
2020. Subsequent surveys conducted along the Israeli shore in summer 2020 revealed
patchy but dense aggregations at several locations. An opportunistic species, ecosystem
engineer, and fouling threat with rapid growth rate, the profuse presence of P. perna on
the Mediterranean Israeli coast raised the possibility of ramifications for intertidal
community structure.
The study set out to document and compare the status of P. perna population at four sites,
comprising basic data on population density, size structure, growth rate, and epibiota
within one year of their initial detection. The study plan was upended by an
unprecedented heatwave that annihilated the entire population at the sampled sites and
throughout the Israeli coastline.
Materials and methods
Samples for population size structure analyses were collected at four sites, spanning
approximately 140 km of coastline. Samples from Haifa A (32°49′59.4″N; 35°03′04.2″E) and
Ashdod B (31°44′49.5″N; 34°36′03.6″E) were collected from semi-isolated small rocky
outcrops separated by shallow troughs from public bathing beaches; from Ashdod A, a stretch
of beach rock situated north of Ashdod Port (31°51′16.5″N; 34°39′39.3″E) and from Haifa B,
concrete barrier blocks protecting the seaward fence of the Petroleum and Energy
Infrastructures (PEI) facility, adjacent to Haifa port (32°49′35.1″N; 35°02′42.8″E). Mussels
were scraped from within three randomly placed replicate 30 × 30 cm quadrates in June 2021.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
95