Hoopoe – A blog by nhbs

As an island nation, the shoreline around the British Isles has a special significance for many of us. Whilst we might feel at home combing rockpools or wandering the shoreline, the world of plankton remains far more elusive.

In Seashore Plankton, Julian Cremona, author, educator, and naturalist, reveals the fascinating microscopic life found in our coastal waters. Perfect for naturalists, ecologists, and students, Seashore Plankton is the first practical, shore-based guide to collecting and identifying marine plankton. Packed with over 400 vivid photographs and clear advice on sampling and microscopy, the book opens an unseen world while highlighting the ecological importance—and vulnerability—of these tiny organisms.

Ahead of the publication, we had the opportunity to talk with Julian about the book’s development.

Firstly, can you tell us a little bit about your background and the reasons for writing this book? 

I have always had a fascination with biodiversity in all ecosystems, and have been collecting marine and freshwater plankton since the late 1970s.  After nearly sixty years of educating people in seashore ecology, I know how important plankton knowledge is to fundamentally understand the complexity of the shore. There are a few good books and papers about identifying offshore planktonic species, but they are scientific works and do not look at collecting, studying, or interactions between organisms. Most importantly, there are none dedicated to the seashore. 

Plankton collected directly from the seashore is different from that taken offshore. There is some overlap and so the identification books that exist are useful, but there is nothing out there that is specific. The water lapping over the seashore has a more biodiverse variety of organisms compared to offshore samples. This is because the plankton arrives from three or four different sources: rivers and estuaries, invertebrate larvae released from the seashore, organisms washed by wave action into the plankton and life brought in by wind and tides from the ocean. I felt a whole new approach was needed to make seashore plankton accessible and try to unravel its complexity. In particular, I wanted to describe how to collect samples from the shore rather than a boat, explain how to look at them, and introduce the huge array of organisms found on the shore and how they link with the life that we can more easily observe.  

I have written a number of books on the seashore, but this was the most difficult. Part of the problem is that you are writing about creatures that few people have seen or can comprehend, especially because most do not have common names. It is surprising how many people can be expert on seashores but still be unclear on the microscopic plankton that is an essential part of the ecology.

Oriental Shrimp. Image by Julian Cremona.

 In the introduction, you discuss how difficult it is for us as terrestrial creatures to understand the ocean as a complex ecosystem. How has your understanding of the seashore as an ecosystem changed throughout your study? 

Whenever I stop near the coast and look out at a vast expanse of blue, I invariably think of the trillions of organisms out of our sight, to which most people would not give a thought.  

Over the years there have been subtle changes in how I study the seashore. In the last decade or so I have tried to bridge the gap between the organisms we see with the naked eye, like, say, sea anemones, and the microscopic detail of the plankton. For example, small pieces of glass and other materials placed on the shore will quickly become colonised by spores and larvae from the plankton over time. By removing these pieces to observe the developing biofilms under low magnification and photographing changes, it has given me a better insight into the relationship between substrate, tides and the organisms. The change in the first few weeks is amazing with the growth of bacteria, forming long chains, enabling diatoms and protists to begin colonisation. The more I observe, the more I realise how little we understand.

You point out the assumption that specialist or expensive gear is required to observe seashore plankton. How does someone interested in coastal plankton get started?

Collecting from the shore requires different considerations. Trawling from a boat is easier, for one thing. To collect a sample, a large volume of water needs to be filtered for microscopic life, and there are different ways to do that. Buying a good net to pull through the water is the best option, but then finding a suitable place for sampling can be a challenge. All this is covered in the book: where to sample, and how to choose and use the net. An expensive microscope is unnecessary, and the book tries to give some suggestions for observation, but you will need some way of magnifying the creatures found. Most other items you need are inexpensive and may well be in your home already.   

I was recently amazed to learn the role that phytoplankton play in oxygen production. What else has the study of plankton revealed about oceanic and planetary systems, and how are plankton linked to human and planetary well-being? 

One misnomer, that one sees regularly stated, is that every second breath you take is oxygen from phytoplankton. For sure, 50% of the oxygen produced on earth is from phytoplankton but mostly that stays in the sea and is used by the organisms living there. We are still reliant on terrestrial sources of oxygen. The study of plankton and links to our wellbeing is a huge topic and only briefly discussed in the book. If I choose one example, it is probably how common species within marine plankton have an essential role in sequestering carbon and taking it to the bottom of the oceans. So few people in the world realise how important the sea is in determining our weather patterns, and plankton is part of that – a reason why plankton blooms are monitored by NASA from space. 

A large portion of the book is devoted to the dizzying array of organisms that can be found within the plankton. Is there a group you find yourself particularly drawn to? 

Marine worms, the polychaetes, have species that permanently live in the plankton that I love finding. Huge numbers of other worm species live in sediment or on rocky seashores and liberate amazing larval forms that develop and grow for weeks in the plankton. Some, like the syllids, have a weird sexual reproduction called epitoky where the worm on the shore grows a special new ‘worm’ (called a stolon) on the end of the body that can be male or female. These swim off into the plankton to find a mate and disperse but eventually die as they have no gut. I love the diversity and beauty of the polychaetes. One of the most common larvae found are those of Polydora, which change dramatically over time and are super to watch, with real character.  

The final chapter discusses the human induced stressors on the ocean ecosystems and plankton populations, from pollution to climate change. Can you give us an idea of some of the changes, and have you been able to observe any over the course of your study? 

The most obvious issue is that of the warming sea along the coast. We can surmise some of the problems, like the increase in jellyfish, but will the synchrony between copepods (important crustaceans as prey for fish) and the organisms they feed on change? We know this is happening on land, for example where nesting insectivorous birds may produce young before the appearance of insect prey. Acidification of the oceans was predicted many decades ago, but already problems are developing where some mollusc larvae are failing to develop shells properly. 

In the last few years, we have seen the sea around Milford Haven, where I sample, reach record high temperatures. There are two noticeable long-term anecdotal changes I have noticed in the last decade. One is the increase in ‘gelatinous plankton’, not just jellyfish but also small hydromedusae and siphonophores. The most well-known of the latter is the infamous Portuguese Man-o’-war, but there are also many much smaller, completely transparent (and thus difficult to see) forms, that congregate in huge numbers during the summer. The second observation is in the composition of plankton. While many species occur year after year there are steadily more warm water species appearing as distribution ranges move northwards.    

And finally, do you have any other projects on the horizon? 

As I said at the start, I enjoy observing all ecosystems. One that has always fascinated me is the saltmarsh. These are great breeding grounds for microscopic life. Sometimes this can temporarily appear in marine plankton, and I have been drawn to sampling the surface mud in all areas of the marsh as well as the saltpan pools that vary so much in their salinity. This is an area I am developing and intend to spend more time studying. 

Seashore Plankton; A Practical Introduction to Biology and Identification
can be ordered here.

NHBS Ltd. Produces and supplies a variety of plankton nets and accessories, to be used from the shoreside or on open water. Browse our catalogue here to find the net to suit your project.

More books by Julian Cremona:

In the recently released Rocky Shores, Julian Cremona unleashes his passion and expertise on the boulder-strewn shores of the British coastline. Covering the life of rock pools and strandlines, including molluscs, worms, seaweeds, invertebrates, and microbes, this is a must-have for shore lovers.

Seashores An Ecological Guide.
A user-friendly, authoritative reference featuring over 400 color photos of common coastal organisms. It explores key species, their adaptations, and how they survive environmental stresses across diverse habitats like rocky shores, sand and mud, estuaries, salt marshes, sand dunes, shingle, and plankton.

Extreme Close-Up Photography and Focus Stacking
A practical guide to capturing detailed macro shots, from butterfly wings to eyes. It covers affordable techniques for photographing terrestrial, marine, and freshwater subjects, with clear instructions for outdoor and studio settings. Special attention is given to focus stacking, software use and enhancements.