The tidal zone of the Azores changes its appearance between high and low tide, revealing a stretch of coastline twice a day. Its extent varies depending on the type of shore and the height of the tide—greater during the New Moon and Full Moon, and smaller during the First and Last Quarter phases. Atmospheric pressure and wind can also influence tidal range. Beyond this zone lies the permanently submerged area.

For marine organisms, the tidal zone is a demanding environment. Plants and animals living here are exposed to air, extreme temperature fluctuations, sudden changes in salinity, and constant wave and current action. The level of wave exposure can significantly shape the structure of local communities.

In more sheltered areas, marine algae can grow abundantly. In the Azores, however, such conditions are rare and mostly limited to harbors, as the coastline is generally exposed to strong wave action. As a result, shores are dominated by small-sized algae and barnacles. More resistant crustose forms—algae that grow flat and firmly attached to the substrate—prevail in many areas, while larger, leaf-like algae are mostly confined to tidal pools.

The best way to observe these organisms is during low tide walks along the coast, or through snorkeling and scuba diving. A careful look reveals a remarkable diversity of colors, shapes, and sizes. Research conducted over the past two decades has significantly expanded our understanding of Azorean marine macroalgae.

Diversity and Observation

There are around 400 species of marine macroalgae in the Azores. While the larger ones are easy to spot, many species are only visible with the help of a magnifying glass or microscope.

These organisms, often overlooked, play a fundamental role in coastal ecosystems and contribute significantly to the biological richness of the islands.