The Havana littoral, an area of distribution for Physalia physalis in the Atlantic Ocean

Abstract

The hydrozoan Portuguese man-of-war (Physalia physalis) is distributed throughout the Havana littoral zone, which is one of the circulation points of the currents that form the North Atlantic Subtropical Gyre run. For the first time, a study was conducted monthly from May 2018 through May 2019 to better understand the temporal and spatial variation of P. physalis in this region. This study covered five beaches in Havana (Cojímar, Bacuranao, Tarará, Mégano and Santa María). Transects of 50 m were located parallel to the shoreline and the colonies that arrived at the intertidal zone were counted. The colonies of P. physalis were mostly observed in May 2018 (80), November 2018 (110), December 2018 (132), January 2019 (152) and March 2019 (126), which coincided with the dry season in Cuba. This season was related to the presence of cold fronts and a negative average magnitude of the Arctic Oscillation Index (-0.05). The beaches with a relatively linear shape had a higher number of arrivals (549 colonies) than the beaches with a horseshoe shape (109 colonies). In addition, the highest number of colonies was associated with wind velocity above 33 km.h⁻¹ (especially northerly wind), wave height above 1.5 m, and temperatures below 30 °C.

Introduction

Physalia physalis Linnaeus, 1758 (phylum: Cnidaria, class: Hydrozoa, order: Siphonophora, family: Physaliidae), also known as the Portuguese man-of-war or blue bottle, is a colony formed by numerous polyps (Mapstone, 2014). It is a pleustonic and cosmopolitan pelagic species that move with surface currents and winds (Ferrer and Pastor, 2017). These colonies are typical of tropical and subtropical warm waters (Ferrer and Pastor, 2017). According to Ferrer and Pastor (2017), P. physalis colonies are commonly found in Florida, USA, the Gulf Stream, the Gulf of Mexico, the Caribbean Sea and the Sargasso Sea, although they are a native species of the Pacific and Indian Oceans (Kirkpatrick and Pugh, 1984), where they can also be found. In the Mediterranean Sea, P. physalis is an allochthonous species (Prieto et al., 2015). The appearance of colonies on the coasts is due to temporary meteorological/oceanographic changes, such as the El Niño phenomenon in the Pacific Ocean, which modify the direction and speed of the winds (Prieto et al., 2015). The North Atlantic Oscillation index (NAOi) and the Arctic Oscillation index (AOi) are one of the major modes of variability in the Northern Hemisphere atmosphere and they are especially significant in winter (December to March) according to Prieto et al. (2015) and Cedeño (2015). Both indices perform a strong control on the climate of Atlantic Ocean by regulating the intensity of zonal winds and precipitation patterns (Barnston and Livezey, 1987, Cedeño, 2015). Prieto et al. (2015) used the NAOi as a measure to explain specific oceanographic and climatic conditions that led to the occurrence of the P. physalis within the Mediterranean basin in summer 2010. Moreover, the AOi has been used as a measure of frequency and intensity of cold fronts in Western Cuba (Cedeño, 2015), but has not yet been used for P. physalis distribution.

As other jellyfishes, the species P. physalis plays a crucial ecological role in aquatic ecosystems, since they are important for the recycling of nutrients, such as carbon, nitrogen, and phosphorous, which are subsequently used by phytoplankton (Ponce García and López Vera, 2013). Codon et al. (2012) stated that when a jellyfish bloom occurs, the carbon contained in the ecosystems near the shoreline could be much higher than the carbon flux under normal conditions. Pitt et al. (2014) argued that a mass of stranding and decaying medusa on the beach can increase the input of carbon to beach environments, given that these are poorly productive sites. It is also worth mentioning that many species of jellyfish and hydrozoans serve as food for birds, chum salmon, spiny dogfishes, and sea turtles (Pitt et al., 2014), such as the leatherback turtle (Dermochelys coriacea Vandelli, 1761), which is a compulsory consumer of gelatinous zooplankton (Ponce García and López Vera, 2013). However, overfishing affects the presence of many fishes and sea turtles, which have decreased markedly according to Mazaris et al. (2017), with a possible consequence for the abundance of jellyfishes.

One of the most common problems on the shoreline is the appearance of jellyfishes and other gelatinous organisms, such as P. physalis. They can cause a relevant socio-economic impact, mainly in sun and beach tourism (Ferrer et al., 2015). The Portuguese man-of-war may have systematic effects on humans: cardiovascular, respiratory, neurological, gastrointestinal, renal and hematological/immunological (Martínez et al., 2010). Prieto et al. (2015) have reported the death of a person in the Mediterranean Sea, caused by a P. physalis sting.

Ferrer and Pastor (2017) describe a northern region of the North Atlantic Subtropical Gyre (NASG) as a possible origin of the Portuguese man-of-war, and the importance of the appearance of atypical weather conditions for unusual arrivals to the Bay of Biscay. Prieto et al. (2015) suggested that the arrival of P. physalis at the Eastern Atlantic coast and later on in the Mediterranean Sea, entering through the Strait of Gibraltar, may be due to the action of the currents that make up the NASG, under specific climatic and oceanographic conditions that also modify the wind patterns. In recent years, the arrival of these colonies have been seen more frequently not only on the coasts of the Caribbean Sea but also in the Eastern Atlantic, although the causes remain to be identified. Longer time series and additional monitoring points on both sides of the Atlantic Ocean will be the key to untangling the variability of these colonies and minimizing the social-economic impact by improving forecasting systems.

For a better understanding of the arrival of P. physalis at one of the zones where the currents of the NASG run, we analyzed the spatial and temporal variations of P. physalis on five beaches in Havana, Cuba, during one year. The principal aim of this study was to analyze the beaching dynamics of these colonies with the associated environmental variables, and to contribute for the first time on a high temporal resolution (monthly) to their monitoring in the Western Atlantic Ocean.