# 3.4 Harmful algal blooms

Some CDR methods also have risks. One is rapid escape of stored CO2 into the atmosphere, reducing its effectiveness.

Iron fertilisation may harm marine ecosystems: for example, by creating ‘red tides’ of harmful algae (Figure 7). Such a red tide in 2013 was reported to have killed 276 manatees in Florida (Brown, 2013). Red tides also pose a risk to human health through eating contaminated shellfish.

Figure 7 A ‘red tide’ – the common name for a harmful algal bloom of toxic types of phytoplankton – this one is near Cape Rodney, New Zealand.

OpenLearn - Could we control our climate?
Except for third party materials and otherwise, this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence, full copyright detail can be found in the acknowledgements section. Please see full copyright statement for details.