Still waiting for Porpoises and Sea Sparkles

The sun was shining strongly in my neck through the car window, while I was driving through the landscape of Goeree-Overflakkee, South-Holland. I was on my way to the harbour of Stellendam for another evening trip on the Voordelta, with temperatures rising above 30 Degrees Celsius. The sunburn in my neck was annoying me greatly and I was happy to arrive in the harbour to cool down in the shadows. There was only a slight breeze NNW, the sky was very clear and the waves were at a slow pace reaching about 10-16 centimeters high. Perfect weather conditions to spot Harbour Porpoises, you might think. 

Honestly... it's not really the season to spot them: sightings since the early 1970s  show that coastal habitats are more frequently visited by porpoises in Winter and in Spring. In some regions Harbour Porpoises are seen year-round except for mid-Summer. The migrations of Harbour Porpoises and the seasonality seem to suggest that they are highly mobile throughout the year. This means: they move around a lot from one coastal zone to another. A small resident population of Harbour Porpoises is present in the Delta-region of the Netherlands, with the highest density in the Oosterschelde. It's only since 2001 that an increase of sightings in the Delta occured (Camphuysen & Siemensma 2011). 

The captain of the Sirius and his crew spotted four Harbour Porpoises the day before my trip, though a bit further away from the coastline. In the Delta-region Harbour Porpoises do migrate into the shallows year-round, but less frequently during Summer. This trip the porpoises did not show... however, there was an abundance of gulls closing in on the Sirius, particularly Lesser Black-backed Gulls, Common Gulls and Common Terns. Great Black-backed Gulls were seen on the water and the peninsula.

Lesser Black-backed Gulls

From the birds to marine phenomena... During the trip I was hoping for a special moment: on July 24th -25th there was a very intriguing phenomena visible across the Dutch coast, red tides of the algae Noctiluca scintillans, a dinoflagellate that is also referred to as Sea Sparkle due to it's capacity of bioluminescense. This means that the sea will light up with blue-green lights caused by the waves as disturbance of the algae. Marko of Delta Safari told me the news of the recent occurrence of the phenomena across the Dutch coast during the trip, and silently I was hoping to see it after the sunset when it gets dark. (I wrote about red tides and blue-green bioluminescense before, see my former blogpost.)*

Well... you might be wondering if I saw the sea sparkles? I didn't get lucky either to see this phenomena, though the predictions were favourable. Overall I must say: sometimes you get lucky, and sometimes you don't! It comes with the profession. So I am still waiting for the porpoises and the sea sparkles.

The next trip of Delta Safari starts on July 31st, a whole day trip with the Sirius. You can still attend, go to www.deltasafari.nl

* I do need to note that some red tides of dinoflagellates can be toxic, while others are not. It depends on which species is accountable for this bloom of algae. Noctiluca scintillans is harmless, while the Alexandrium species are quite the opposite.

Literature

Camphuysen CJ & Siemensma ML (2011) Conservation plan for the Harbour Porpoise Phocoena phocoena in the Netherlands: towards a favourable conservation status. NIOZ Report 2011-07, Royal Netherlands Institute for Sea Research, Texel.

Camphuysen CJ & Peet G (2006) Walvissen en dolfijnen in de Noordzee, Fontaine Uitgevers BV 's-Gravenland /Stichting De Noordzee Utrecht.